%%% -*-BibTeX-*- %%% ==================================================================== %%% BibTeX-file{ %%% author = "Nelson H. F. Beebe", %%% version = "1.54", %%% date = "15 March 2017", %%% time = "16:47:54 MST", %%% filename = "tocl.bib", %%% address = "University of Utah %%% Department of Mathematics, 110 LCB %%% 155 S 1400 E RM 233 %%% Salt Lake City, UT 84112-0090 %%% USA", %%% telephone = "+1 801 581 5254", %%% FAX = "+1 801 581 4148", %%% URL = "http://www.math.utah.edu/~beebe", %%% checksum = "42126 16756 86500 834921", %%% email = "beebe at math.utah.edu, beebe at acm.org, %%% beebe at computer.org (Internet)", %%% codetable = "ISO/ASCII", %%% keywords = "bibliography, BibTeX, ACM Transactions on %%% Computational Logic", %%% license = "public domain", %%% supported = "yes", %%% docstring = "This is a COMPLETE BibTeX bibliography for %%% the journal ACM Transactions on Computational %%% Logic (no CODEN, ISSN 1529-3785), for %%% 2000--date. %%% %%% Publication began with volume 1, number 1, in %%% July 2000. The journal appears quarterly. %%% %%% The journal has a World-Wide Web site at: %%% %%% http://www.acm.org/pubs/tocl %%% http://tocl.acm.org %%% %%% Tables-of-contents of all issues are %%% available at: %%% %%% http://www.acm.org/pubs/contents/journals/tocl/ %%% http://portal.acm.org/browse_dl.cfm?idx=J773 %%% %%% Qualified subscribers can retrieve the full %%% text of recent articles in PDF form. %%% %%% At version 1.54, the COMPLETE journal %%% coverage looked like this: %%% %%% 2000 ( 12) 2006 ( 24) 2012 ( 34) %%% 2001 ( 21) 2007 ( 31) 2013 ( 34) %%% 2002 ( 18) 2008 ( 22) 2014 ( 34) %%% 2003 ( 21) 2009 ( 36) 2015 ( 43) %%% 2004 ( 23) 2010 ( 30) 2016 ( 25) %%% 2005 ( 28) 2011 ( 21) %%% %%% Article: 457 %%% %%% Total entries: 457 %%% %%% The initial draft of this bibliography was %%% derived from data at the ACM Web site. %%% %%% ACM copyrights explicitly permit abstracting %%% with credit, so article abstracts, keywords, %%% and subject classifications have been %%% included in this bibliography wherever %%% available. %%% %%% The bibsource keys in the bibliography %%% entries below indicate the data sources. %%% %%% URL keys in the bibliography point to %%% World Wide Web locations of additional %%% information about the entry. %%% %%% Spelling has been verified with the UNIX %%% spell and GNU ispell programs using the %%% exception dictionary stored in the %%% companion file with extension .sok. %%% %%% BibTeX citation tags are uniformly chosen %%% as name:year:abbrev, where name is the %%% family name of the first author or editor, %%% year is a 4-digit number, and abbrev is a %%% 3-letter condensation of important title %%% words. Citation tags were automatically %%% generated by software developed for the %%% BibNet Project. %%% %%% In this bibliography, entries are sorted in %%% publication order, using ``bibsort -byvolume.'' %%% %%% The checksum field above contains a CRC-16 %%% checksum as the first value, followed by the %%% equivalent of the standard UNIX wc (word %%% count) utility output of lines, words, and %%% characters. This is produced by Robert %%% Solovay's checksum utility.", %%% } %%% ====================================================================

@Preamble{"\input bibnames.sty"}

%%% ==================================================================== %%% Acknowledgement abbreviations:

@String{ack-nhfb= "Nelson H. F. Beebe, University of Utah, Department of Mathematics, 110 LCB, 155 S 1400 E RM 233, Salt Lake City, UT 84112-0090, USA, Tel: +1 801 581 5254, FAX: +1 801 581 4148, e-mail: \path|beebe@math.utah.edu|, \path|beebe@acm.org|, \path|beebe@computer.org| (Internet), URL: \path|http://www.math.utah.edu/~beebe/|"}

%%% ==================================================================== %%% Journal abbreviations:

@String{j-TOCL= "ACM Transactions on Computational Logic"}

%%% ==================================================================== %%% Publisher abbreviations:

@String{pub-ACM= "ACM Press"} @String{pub-ACM:adr= "New York, NY 10036, USA"}

%%% ==================================================================== %%% Bibliography entries:

@Article{Paulson:2000:MUI, author = "Lawrence C. Paulson", title = "Mechanizing {UNITY} in {Isabelle}", journal = j-TOCL, volume = "1", number = "1", pages = "3--32", month = jul, year = "2000", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Oct 13 11:28:38 MDT 2000", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/articles/journals/tocl/2000-1-1/p3-paulson/p3-paulson.pdf; http://www.acm.org/pubs/citations/journals/tocl/2000-1-1/p3-paulson/", abstract = "UNITY is an abstract formalism for proving properties of concurrent systems, which typically are expressed using guarded assignments [Chandy and Misra 1988]. UNITY has been mechanized in higher-order logic using Isabelle, a proof assistant. Safety and progress primitives, their weak forms (for the substitution axiom), and the program composition operator (union) have been formalized. To give a feel for the concrete syntax, this article presents a few extracts from the Isabelle definitions and proofs. It discusses a small example, two-process mutual exclusion. A mechanical theory of unions of programs supports a degree of compositional reasoning. Original work on extending program states is presented and then illustrated through a simple example involving an array of processes.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "compositional reasoning; concurrency; Isabelle; UNITY", subject = "Theory of Computation --- Logics and Meanings of Programs --- Specifying and Verifying and Reasoning about Programs (F.3.1)", } @Article{Libkin:2000:LCL, author = "Leonid Libkin", title = "Logics with counting and local properties", journal = j-TOCL, volume = "1", number = "1", pages = "33--59", month = jul, year = "2000", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Oct 13 11:28:38 MDT 2000", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/citations/journals/tocl/2000-1-1/p33-libkin/", abstract = "The expressive power of first-order logic over finite structures is limited in two ways: it lacks a recursion mechanism, and it cannot count. Overcoming the first limitation has been a subject of extensive study. A number of fixpoint logics have been introduced. and shown to be subsumed by an infinitary logic L w w. This logic is easier to analyze than fixpoint logics, and it still lacks counting power, as it has a 0-1 law. On the counting side, there is no analog of L w w. There are a number of logics with counting power, usually introduced via generalized quantifiers. Most known expressivity bounds are based on the fact that counting extensions of first-order logic preserve the locality properties. This article has three main goals. First, we introduce a new logic L * w ( C ) that plays the same role for counting as L w w does for recursion--it subsumes a number of extensions of first-order logic with counting, and has nice properties that make it easy to study. Second, we give simple direct proof that L w w ( C ) expresses only local properties: those that depend on the properties of small neighborhoods, but cannot grasp a structure as a whole. This is a general way of saying that a logic lacks a recursion mechanism. Third, we consider a finer analysis of locality of counting logics. In particular, we address the question of how local a logic is, that is, how big are those neighborhoods that local properties depend on. We get a uniform answer for a variety of logics between first-order and L * w ( C ). This is done by introducing a new form of locality that captures the tightest condition that the duplicator needs to maintain in order to win a game. We also use this technique to give bounds on outputs of L * w (C)-definable queries.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "counting; first-order logic; infinitary logic; locality", subject = "Theory of Computation --- Mathematical Logic and Formal Languages --- Mathematical Logic (F.4.1)", } @Article{Kozen:2000:HLK, author = "Dexter Kozen", title = "On {Hoare} logic and {Kleene} algebra with tests", journal = j-TOCL, volume = "1", number = "1", pages = "60--76", month = jul, year = "2000", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Oct 13 11:28:38 MDT 2000", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/citations/journals/tocl/2000-1-1/p60-kozen/", abstract = "We show that Kleene algebra with tests (KAT) subsumes propositional Hoare logic (PHL). Thus the specialized syntax and deductive apparatus of Hoare logic are inessential and can be replaced by simple equational reasoning. In addition, we show that all relationally valid inference rules are derivable in KAT and that deciding the relational validity of such rules is {\em PSPACE}-complete.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "dynamic logic; Hoare logic; Kleene algebra; Kleene algebra with tests; specification", subject = "Software --- Software Engineering --- Design Tools and Techniques (D.2.2): {\bf Structured programming**}; Software --- Software Engineering --- Software/Program Verification (D.2.4): {\bf Correctness proofs}; Software --- Programming Languages --- Language Constructs and Features (D.3.3): {\bf Control structures}; Theory of Computation --- Logics and Meanings of Programs --- Specifying and Verifying and Reasoning about Programs (F.3.1): {\bf Assertions}; Theory of Computation --- Logics and Meanings of Programs --- Specifying and Verifying and Reasoning about Programs (F.3.1): {\bf Invariants}; Theory of Computation --- Logics and Meanings of Programs --- Specifying and Verifying and Reasoning about Programs (F.3.1): {\bf Logics of programs}; Theory of Computation --- Logics and Meanings of Programs --- Specifying and Verifying and Reasoning about Programs (F.3.1): {\bf Mechanical verification}; Theory of Computation --- Logics and Meanings of Programs --- Specifying and Verifying and Reasoning about Programs (F.3.1): {\bf Pre- and post-conditions}; Theory of Computation --- Logics and Meanings of Programs --- Specifying and Verifying and Reasoning about Programs (F.3.1): {\bf Specification techniques}; Theory of Computation --- Logics and Meanings of Programs --- Semantics of Programming Languages (F.3.2): {\bf Algebraic approaches to semantics}; Theory of Computation --- Logics and Meanings of Programs --- Studies of Program Constructs (F.3.3): {\bf Control primitives}; Computing Methodologies --- Symbolic and Algebraic Manipulation --- Expressions and Their Representation (I.1.1): {\bf Simplification of expressions}; Computing Methodologies --- Symbolic and Algebraic Manipulation --- Languages and Systems (I.1.3): {\bf Special-purpose algebraic systems}; Computing Methodologies --- Artificial Intelligence --- Automatic Programming (I.2.2): {\bf Program modification}; Computing Methodologies --- Artificial Intelligence --- Automatic Programming (I.2.2): {\bf Program transformation}; Computing Methodologies --- Artificial Intelligence --- Automatic Programming (I.2.2): {\bf Program synthesis}; Computing Methodologies --- Artificial Intelligence --- Automatic Programming (I.2.2): {\bf Program verification}", } @Article{Gurevich:2000:SAS, author = "Yuri Gurevich", title = "Sequential abstract-state machines capture sequential algorithms", journal = j-TOCL, volume = "1", number = "1", pages = "77--111", month = jul, year = "2000", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Oct 13 11:28:38 MDT 2000", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/citations/journals/tocl/2000-1-1/p77-gurevich/", abstract = "We examine sequential algorithms and formulate a sequential-time postulate, an abstract-state postulate, and a bounded-exploration postulate. Analysis of the postulates leads us to the notion of sequential abstract-state machine and to the theorem in the title. First we treat sequential algorithms that are deterministic and noninteractive. Then we consider sequential algorithms that may be nondeterministic and that may interact with their environments.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "abstract-state machine; executable specification; sequential algorithm; sequential ASM thesis; specification; Turing's thesis", subject = "Theory of Computation --- Computation by Abstract Devices --- Models of Computation (F.1.1); Computing Methodologies --- Simulation and Modeling --- Model Development (I.6.5): {\bf Modeling methodologies}", } @Article{Grohe:2000:LOI, author = "Martin Grohe and Thomas Schwentick", title = "Locality of order-invariant first-order formulas", journal = j-TOCL, volume = "1", number = "1", pages = "112--130", month = jul, year = "2000", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Oct 13 11:28:38 MDT 2000", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/citations/journals/tocl/2000-1-1/p112-grohe/", abstract = "A query is {\em local\/} if the decision of whether a tuple in a structure satisfies this query only depends on a small neighborhood of the tuple. We prove that all queries expressible by {\em order-invariant\/} first-order formulas are local.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "first-order logic; locality; logics; ordered structures", subject = "Theory of Computation --- Mathematical Logic and Formal Languages --- Mathematical Logic (F.4.1)", } @Article{Liberatore:2000:CCR, author = "Paolo Liberatore", title = "Compilability and compact representations of revision of {Horn} knowledge bases", journal = j-TOCL, volume = "1", number = "1", pages = "131--161", month = jul, year = "2000", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Oct 13 11:28:38 MDT 2000", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/citations/journals/tocl/2000-1-1/p131-liberatore/", abstract = "Several methods have been proposed as an attempt to deal with dynamically changing scenarios. From a computational point of view, different formalisms have different computational properties. In this article we consider knowledge bases represented as sets of Horn clauses. The importance of this case is twofold: first, inference is polynomial, thus tractable; second, Horn clauses represents causal relations between facts, thus they are of great practical importance, although not all propositional knowledge bases can be represented in Horn form. The complexity of Horn revision is still high, and in some cases coincides with the complexity of the general (non-Horn) case. We analyze the complexity of belief revision from the point of view of the compilation [Cadoli et al. 1999]: we study the possibility of reducing the complexity by allowing a (possibly expensive) preprocessing of part of the input of the problem. Extending the work of Cadoli et al.[1996], we consider the problem of compact representation of revision in the Horn case, i.e., given a knowledge base $T$ and an update $P$ (both represented by Horn clauses) decide whether $T * P$, the result of the revision, can be represented with a propositional formula whose size is polynomial in the size of $T$ and $P$. We give this representation for all formalisms for which it exists, and we show that the existence of a compact representation is related to the possibility of decreasing the complexity of a formalism via a preprocessing.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "compact representations; compilability", subject = "Theory of Computation --- Computation by Abstract Devices --- Complexity Measures and Classes (F.1.3): {\bf Reducibility and completeness}; Computing Methodologies --- Artificial Intelligence --- Deduction and Theorem Proving (I.2.3): {\bf Nonmonotonic reasoning and belief revision}; Computing Methodologies --- Artificial Intelligence --- Knowledge Representation Formalisms and Methods (I.2.4)", } @Article{Aziz:2000:MCC, author = "Adnan Aziz and Kumud Sanwal and Vigyan Singhal and Robert Brayton", title = "Model-checking continuous-time {Markov} chains", journal = j-TOCL, volume = "1", number = "1", pages = "162--170", month = jul, year = "2000", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Oct 13 11:28:38 MDT 2000", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/citations/journals/tocl/2000-1-1/p162-aziz/", abstract = "We present a logical formalism for expressing properties of continuous-time Markov chains. The semantics for such properties arise as a natural extension of previous work on discrete-time Markov chains to continuous time. The major result is that the verification problem is decidable; this is shown using results in algebraic and transcendental number theory.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "formal verification; model checking; real time; transcendental number theory", subject = "Theory of Computation --- Logics and Meanings of Programs --- Specifying and Verifying and Reasoning about Programs (F.3.1): {\bf Logics of programs}; Computer Systems Organization --- Computer-Communication Networks --- Network Protocols (C.2.2): {\bf Protocol verification}; Mathematics of Computing --- Numerical Analysis --- Roots of Nonlinear Equations (G.1.5): {\bf Systems of equations}; Mathematics of Computing --- Probability and Statistics (G.3): {\bf Stochastic processes}; Software --- Software Engineering --- Software/Program Verification (D.2.4): {\bf Model checking}", } @Article{Cohen:2000:NCP, author = "Ernie Cohen and Dexter Kozen", title = "A note on the complexity of propositional {Hoare} logic", journal = j-TOCL, volume = "1", number = "1", pages = "171--174", month = jul, year = "2000", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Oct 13 11:28:38 MDT 2000", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/citations/journals/tocl/2000-1-1/p171-cohen/", abstract = "We provide a simpler alternative proof of the {\em PSPACE\/} -hardness of propositional Hoare logic (PHL).", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Hoare logic; specification", subject = "Software --- Software Engineering --- Design Tools and Techniques (D.2.2): {\bf Structured programming**}; Software --- Software Engineering --- Software/Program Verification (D.2.4): {\bf Correctness proofs}; Software --- Programming Languages --- Language Constructs and Features (D.3.3): {\bf Control structures}; Theory of Computation --- Logics and Meanings of Programs --- Specifying and Verifying and Reasoning about Programs (F.3.1): {\bf Assertions}; Theory of Computation --- Logics and Meanings of Programs --- Specifying and Verifying and Reasoning about Programs (F.3.1): {\bf Invariants}; Theory of Computation --- Logics and Meanings of Programs --- Specifying and Verifying and Reasoning about Programs (F.3.1): {\bf Logics of programs}; Theory of Computation --- Logics and Meanings of Programs --- Specifying and Verifying and Reasoning about Programs (F.3.1): {\bf Mechanical verification}; Theory of Computation --- Logics and Meanings of Programs --- Specifying and Verifying and Reasoning about Programs (F.3.1): {\bf Pre- and post-conditions}; Theory of Computation --- Logics and Meanings of Programs --- Specifying and Verifying and Reasoning about Programs (F.3.1): {\bf Specification techniques}; Theory of Computation --- Logics and Meanings of Programs --- Semantics of Programming Languages (F.3.2): {\bf Algebraic approaches to semantics}; Theory of Computation --- Logics and Meanings of Programs --- Studies of Program Constructs (F.3.3): {\bf Control primitives}; Computing Methodologies --- Artificial Intelligence --- Automatic Programming (I.2.2): {\bf Program verification}", } @Article{Friedman:2000:FOC, author = "Nir Friedman and Joseph Y. Halpern and Daphne Koller", title = "First-order conditional logic for default reasoning revisited", journal = j-TOCL, volume = "1", number = "2", pages = "175--207", year = "2000", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Feb 6 09:08:16 MST 2001", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/citations/journals/tocl/2000-1-2/p175-friedman/", abstract = "{\em Conditional logics\/} play an important role in recent attempts to formulate theories of default reasoning. This paper investigates first-order conditional logic. We show that, as for first-order probabilistic logic, it is important not to confound {\em statistical\/} conditionals over the domain (such as ``most birds fly''), and {\em subjective\/} conditionals over possible worlds (such as ``I believe that Tweety is unlikely to fly''). We then address the issue of ascribing semantics to first-order conditional logic. As in the propositional case, there are .many possible semantics. To study the problem in a coherent way, we use {\em plausibility structures}. These provide us with a general framework in which many of the standard approaches can be embedded. We show that while these standard approaches are all the same at the propositional level, they are significantly different in the context of a first-order language. Furthermore, we show that plausibilities provide the most natural extension of conditional logic to the first-order case:we provide a sound and complete axiomatization that contains only the KLM properties and standard axioms of first-order modal logic. We show that most of the other approaches have additional properties, which result in an inappropriate treatment of an infinitary version of the {\em lottery paradox}.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", generalterms = "Theory", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "completeness; conditional logic; default reasoning; first-order logic; KLM properties; plausibility measures", subject = "Theory of Computation --- Mathematical Logic and Formal Languages --- Mathematical Logic (F.4.1): {\bf Modal logic}; Computing Methodologies --- Artificial Intelligence --- Deduction and Theorem Proving (I.2.3): Nonmonotonic reasoning and belief revision; Computing Methodologies --- Artificial Intelligence --- Knowledge Representation Formalisms and Methods (I.2.4): {\bf Modal logic}; Computing Methodologies --- Artificial Intelligence --- Knowledge Representation Formalisms and Methods (I.2.4): {\bf Predicate logic}", } @Article{Dix:2000:PAP, author = "J{\"u}rgen Dix and Mirco Nanni and V. S. Subrahmanian", title = "Probabilistic agent programs", journal = j-TOCL, volume = "1", number = "2", pages = "208--246", year = "2000", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Feb 6 09:08:16 MST 2001", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/citations/journals/tocl/2000-1-2/p208-dix/", abstract = "Agents are small programs that autonomously take actions based on changes in their environment or ``state''. Over the last few years, there has been an increasing number of efforts to build agents that can interact and/or collaborate with other agents. In one of these efforts Eiter et al. [1999] have shown how agents may be built on top of legacy code. However, their framework assumes that agent states are completely determined, and there is no uncertainty in an agent's state. Thus, their framework allows an agent developer to specify how his agents will react when the agent is 100\% sure about what is true/false in the world state. In this paper, we .propose the concept of a {\em probabilistic agent program\/} and show how, given an arbitrary program written in any imperative language, we may build a declarative ``probabilistic'' agent program on top of it which supports decision making in the presence of uncertainty. We provide two alternative semantics for probabilistic programs. We provide sound and complete algorithms to compute the semantics of {\em positive\/} agent programs.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", generalterms = "Theory", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "logic programming; multi-agent reasoning; probabilistic reasoning; uncertainty", subject = "Computing Methodologies --- Artificial Intelligence --- Distributed Artificial Intelligence (I.2.11): {\bf Intelligent agents}; Computing Methodologies --- Artificial Intelligence --- Deduction and Theorem Proving (I.2.3): {\bf Uncertainty, ``fuzzy,'' and probabilistic reasoning}; Computing Methodologies --- Artificial Intelligence --- Knowledge Representation Formalisms and Methods (I.2.4): {\bf Predicate logic}; Computing Methodologies --- Artificial Intelligence --- Knowledge Representation Formalisms and Methods (I.2.4): {\bf Modal logic}; Software --- Software Engineering --- Interoperability (D.2.12); Information Systems --- Database Management --- Systems (H.2.4); Information Systems --- Database Management --- Heterogeneous Databases (H.2.5)", } @Article{Lomuscio:2000:KMS, author = "Alessio R. Lomuscio and Ron van der Meyden and Mark Ryan", title = "Knowledge in multiagent systems: initial configurations and broadcast", journal = j-TOCL, volume = "1", number = "2", pages = "247--284", year = "2000", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Feb 6 09:08:16 MST 2001", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/citations/journals/tocl/2000-1-2/p247-lomuscio/", abstract = "The semantic framework for the modal logic of knowledge due to Halpern and Moses provides a way to ascribe knowledge to agents in distributed and multiagent systems. In this paper we study two special cases of this framework: {\em full systems\/} and {\em hypercubes}. Both model static situations in which no agents has any information about another agent's state. Full systems and hypercubes are an appropriate model for the initial configurations of many systems of interest. We establish a correspondence between full systems and hypercube systems and certain classes of Kripke frames. We show that these classes of systems correspond to the same logic. Moreover, this logic is also the same as that generated by the larger class of {\em weakly directed frames}. We provide a sound and complete axiomatization, S5WD $n$ of this logic, and study its computational complexity. Finally, we show that under certain natural assumptions, in a model where knowledge evolves over time, S5WD $n$ characteristics the properties of knowledge not just at the initial configuration, but also at all later configurations. In this particular, this holds for {\em homogeneous broadcast systems,} which capture settings in which agents are initially ignorant of each others local states, operate synchronously, have perfect recall, and can communicate only by broadcasting.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "completeness; computational complexity", subject = "Theory of Computation --- Mathematical Logic and Formal Languages --- Mathematical Logic (F.4.1): {\bf Modal logic}; Computing Methodologies --- Artificial Intelligence --- Knowledge Representation Formalisms and Methods (I.2.4): {\bf Modal logic}; Computing Methodologies --- Artificial Intelligence --- Distributed Artificial Intelligence (I.2.11): {\bf Multiagent systems}", } @Article{vanHentenryck:2000:SSO, author = "Pascal van Hentenryck and Laurent Perron and Jean-Fran{\c{c}}ois Puget", title = "Search and strategies in {OPL}", journal = j-TOCL, volume = "1", number = "2", pages = "285--320", year = "2000", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Feb 6 09:08:16 MST 2001", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/citations/journals/tocl/2000-1-2/p285-van_hentenryck/", abstract = "OPL is a modeling language for mathematical programming and combinatorial optimization. It is the first language to combine high-level algebraic and set notations from mathematical modeling languages with a rich constraint language and the ability to specify search procedures and strategies that are the essence of constraint programming. This paper describes the facilities available in OPL to specify search procedures. It describes the abstractions of OPL to specify both the search tree (search) and how to explore it (strategies). The paper also illustrates how to use these high-level constructs to implement traditional search procedures in constraint programming and scheduling.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "combinatorial optimization; constraint programming; modeling languages; search", subject = "Software --- Programming Languages (D.3); Software --- Programming Languages --- Language Classifications (D.3.2): {\bf Constraint and logic languages}; Software --- Programming Languages --- Language Constructs and Features (D.3.3): {\bf Constraints}; Software --- Programming Languages --- Language Constructs and Features (D.3.3): {\bf Control structures}", } @Article{Blass:2001:ICL, author = "Andreas Blass and Yuri Gurevich", title = "Inadequacy of computable loop invariants", journal = j-TOCL, volume = "2", number = "1", pages = "1--11", year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jul 25 07:10:50 MDT 2001", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/articles/journals/tocl/2001-2-1/p1-blass/p1-blass.pdf; http://www.acm.org/pubs/citations/journals/tocl/2001-2-1/p1-blass/", abstract = "Hoare logic is a widely recommended verification tool. There is, however, a problem of finding easily checkable loop invariants; it is known that decidable assertions do not suffice to verify while programs, even when the pre- and postconditions are decidable. We show here a stronger result: decidable invariants do not suffice to verify single-loop programs. We also show that this problem arises even in extremely simple contexts. Let $N$ be the structure consisting of the set of natural numbers together with the functions $S(x) = x +1$, $D(x) = 2 (x) = *** x /2***$. There is a single-loop program *** using only three variables $x, y, z$ such that the asserted program $x = y = z = 0$ *** false is partially correct on $N$ but any loop invariant $I(x,y,z)$ for this asserted program is undecidable.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", generalterms = "Algorithms; Theory; Verification", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "assertion; automated deduction; automated reasoning; Hoare logic; loop invariants; postcondition uncomputable; precondition; recursive inseparability", subject = "Theory of Computation --- Logics and Meanings of Programs --- Specifying and Verifying and Reasoning about Programs (F.3.1): {\bf Invariants}", } @Article{Fisher:2001:CTR, author = "Michael Fisher and Clare Dixon and Martin Peim", title = "Clausal temporal resolution", journal = j-TOCL, volume = "2", number = "1", pages = "12--56", year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jul 25 07:10:50 MDT 2001", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/articles/journals/tocl/2001-2-1/p12-fisher/p12-fisher.pdf; http://www.acm.org/pubs/citations/journals/tocl/2001-2-1/p12-fisher/", abstract = "In this article, we examine how clausal resolution can be applied to a specific, but widely used, nonclassical logic, namely discrete linear temporal logic. Thus, we first define a normal form for temporal formulae and show how arbitrary temporal formulae can be translated into the normal form, while preserving satisfiability. We then introduce novel resolution rules that can be applied to formulae in this normal form, provide a range of examples, and examine the correctness and complexity of this approach. Finally, we describe related work and future developments concerning this work.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", generalterms = "Algorithms; Theory; Verification", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "resolution; temporal logic; theorem proving", subject = "Theory of Computation --- Mathematical Logic and Formal Languages --- Mathematical Logic (F.4.1): {\bf Temporal logic}; Computing Methodologies --- Artificial Intelligence --- Deduction and Theorem Proving (I.2.3): {\bf Resolution}", } @Article{Verbaeten:2001:TPL, author = "Sofie Verbaeten and Danny {De Schreye} and Konstantinos Sagonas", title = "Termination proofs for logic programs with tabling", journal = j-TOCL, volume = "2", number = "1", pages = "57--92", year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jul 25 07:10:50 MDT 2001", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/articles/journals/tocl/2001-2-1/p57-verbaeten/p57-verbaeten.pdf; http://www.acm.org/pubs/citations/journals/tocl/2001-2-1/p57-verbaeten/", abstract = "Tabled evaluation is receiving increasing attention in the logic programming community. It avoids many of the shortcomings of SLD execution and provides a more flexible and often considerably more efficient execution mechanism for logic programs. In particular, tabled execution terminates more often than execution based on SLD-resolution. In this article, we introduce two notions of universal termination of logic programming with tabling: quasi-termination and (the stronger notion of) LG-termination. We present sufficient conditions for these two notions of termination, namely quasi-acceptability and LG-acceptability, and we show that these conditions are also necessary in case the selection of tabled predicates meets certain natural criteria. Starting from these conditions, we develop modular termination proofs, i.e., proofs capable of combining termination proofs of separate programs to obtain termination proofs of combined programs. Finally, in the presence of mode information, we state sufficient conditions which form the basis for automatically proving termination in a constraint-based way.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", generalterms = "Languages; Theory", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "prolog; SLG-resolution; tabling", subject = "Software --- Programming Techniques --- Logic Programming (D.1.6); Software --- Programming Techniques --- Automatic Programming (D.1.2); Theory of Computation --- Mathematical Logic and Formal Languages --- Mathematical Logic (F.4.1): {\bf Logic and constraint programming}", } @Article{Bryant:2001:PVU, author = "Randal E. Bryant and Steven German and Miroslav N. Velev", title = "Processor verification using efficient reductions of the logic of uninterpreted functions to propositional logic", journal = j-TOCL, volume = "2", number = "1", pages = "93--134", year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jul 25 07:10:50 MDT 2001", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/articles/journals/tocl/2001-2-1/p93-bryant/p93-bryant.pdf; http://www.acm.org/pubs/citations/journals/tocl/2001-2-1/p93-bryant/", abstract = "The logic of Equality with Uninterpreted Functions (EUF) provides a means of abstracting the manipulation of data by a processor when verifying the correctness of its control logic. By reducing formulas in this logic to propositional formulas, we can apply Boolean methods such as ordered Binary Decision Diagrams (BDDs) and Boolean satisfiability checkers to perform the verification. We can exploit characteristics of the formulas describing the verification conditions to greatly simplify the propositional formulas generated. We identify a class of terms we call ``p-terms'' for which equality comparisons can only be used in monotonically positive formulas. By applying suitable abstractions to the hardware model, we can express the functionality of data values and instruction addresses flowing through an instruction pipeline with p-terms. A decision procedure can exploit the restricted uses of p-terms by considering only ``maximally diverse'' interpretations of the associated function symbols, where every function application yields a different value except when constrained by functional consistency. We present two methods to translate formulas in EUF into propositional logic. The first interprets the formula over a domain of fixed-length bit vectors and uses vectors of propositional variables to encode domain variables. The second generates formulas encoding the conditions under which pairs of terms have equal valuations, introducing propositional variables to encode the equality relations between pairs of terms. Both of these approaches can exploit maximal diversity to greatly reduce the number of propositional variables that need to be introduced and to reduce the overall formula sizes. We present experimental results demonstrating the efficiency of this approach when verifying pipelined processors using the method proposed by Burch and Dill. Exploiting positive equality allows us to overcome the experimental blow-up experienced previously when verifying microprocessors with load, store, and branch instructions.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", generalterms = "Algorithms; Verification", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "decision procedures; processor verification; uninterpreted functions", subject = "Hardware --- Register-Transfer-Level Implementation --- Design Aids (B.5.2): {\bf Verification}; Theory of Computation --- Mathematical Logic and Formal Languages --- Mathematical Logic (F.4.1): {\bf Mechanical theorem proving}", } @Article{Libkin:2001:LCL, author = "Leonid Libkin", title = "Logics capturing local properties", journal = j-TOCL, volume = "2", number = "1", pages = "135--153", year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jul 25 07:10:50 MDT 2001", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/articles/journals/tocl/2001-2-1/p135-libkin/p135-libkin.pdf; http://www.acm.org/pubs/citations/journals/tocl/2001-2-1/p135-libkin/", abstract = "Well-known theorems of Hanf and Gaifman establishing locality of first-order definable properties have been used in many applications. These theorems were recently generalized to other logics, which led to new applications in descriptive complexity and database theory. However, a logical characterization of local properties that correspond to Hanf's and Gaifman's theorems is still lacking. Such a characterization only exists for structures of bounded valence. In this paper, we give logical characterizations of local properties behind Hanf's and Gaifman's theorems. We first deal with an infinitary logic with counting terms and quantifiers that is known to capture Hanf-locality on structures of bounded valence. We show that testing isomorphism of neighborhoods can be added to it without violating Hanf-locality, while increasing its expressive power. We then show that adding local second-order quantification to it captures precisely all Hanf-local properties. To capture Gaifman-locality, one must also add a (potentially infinite) case statement. We further show that the hierarchy based on the number of variants in the case statement is strict.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", generalterms = "Languages; Theory", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "counting; locality; logic", subject = "Theory of Computation --- Mathematical Logic and Formal Languages --- Mathematical Logic (F.4.1)", } @Article{Rybina:2001:DPT, author = "Tatiana Rybina and Andrei Voronkov", title = "A decision procedure for term algebras with queues", journal = j-TOCL, volume = "2", number = "2", pages = "155--181", year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jul 25 07:10:50 MDT 2001", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/articles/journals/tocl/2001-2-2/p155-rybina/p155-rybina.pdf; http://www.acm.org/pubs/citations/journals/tocl/2001-2-2/p155-rybina/", abstract = "In software verification it is often required to prove statements about heterogeneous domains containing elements of various sorts, such as counters, stacks, lists, trees and queues. Any domain with counters, stacks, lists, and trees (but not queues) can be easily seen a special case of the term algebra, and hence a decision procedure for term algebras can be applied to decide the first-order theory of such a domain. We present a quantifier-elimination procedure for the first-order theory of term algebra extended with queues. The complete axiomatization and decidability of this theory can be immediately derived from the procedure.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", generalterms = "Algorithms; Theory; Verification", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "queues; term algebras; trees; words", subject = "Software --- Software Engineering --- Software/Program Verification (D.2.4); Data --- Data Structures (E.1): {\bf Lists, stacks, and queues}; Theory of Computation --- Mathematical Logic and Formal Languages --- Mathematical Logic (F.4.1): {\bf Computational logic}; Computing Methodologies --- Artificial Intelligence --- Deduction and Theorem Proving (I.2.3): {\bf Deduction}", } @Article{Voronkov:2001:HOP, author = "Andrei Voronkov", title = "How to optimize proof-search in modal logics: new methods of proving redundancy criteria for sequent calculi", journal = j-TOCL, volume = "2", number = "2", pages = "182--215", year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jul 25 07:10:50 MDT 2001", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/articles/journals/tocl/2001-2-2/p182-voronkov/p182-voronkov.pdf; http://www.acm.org/pubs/citations/journals/tocl/2001-2-2/p182-voronkov/", abstract = "We present a bottom-up decision procedure for propositional modal logic K based on the inverse method. The procedure is based on the ``inverted'' version of a sequent calculus. To restrict the search space, we prove a number of redundancy criteria for derivations in the sequent calculus. We introduce {\em a new technique\/} of proving redundancy criteria, based on the analysis of tableau-based derivations in K. Moreover, another new technique is based on so-called {\em traces\/}. A new search with a strong notion of subsumption. This technique is based on so-called {\em traces\/}. A new formalization of the inverse method in the form of a {\em path calculus\/} considerably simplifies all proofs as compared to the previously published presentations of the inverse method. Experimental results demonstrate that our method is competitive with many state-of-the-art implementations of K.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", generalterms = "Experimentation; Theory", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "description logics; inverse method; modal logic; proof-search; theorem proving", subject = "Theory of Computation --- Mathematical Logic and Formal Languages --- Mathematical Logic (F.4.1); Computing Methodologies --- Artificial Intelligence --- Knowledge Representation Formalisms and Methods (I.2.4): {\bf Modal logic}", } @Article{Engelfriet:2001:MDS, author = "Joost Engelfriet and Hendrik Jan Hoogeboom", title = "{MSO} definable string transductions and two-way finite-state transducers", journal = j-TOCL, volume = "2", number = "2", pages = "216--254", year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jul 25 07:10:50 MDT 2001", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/articles/journals/tocl/2001-2-2/p216-engelfriet/p216-engelfriet.pdf; http://www.acm.org/pubs/citations/journals/tocl/2001-2-2/p216-engelfriet/", abstract = "We extend a classic result of B{\"u}chi, Elgot, and Trakhtenbrot: MSO definable string transductions i.e., string-to-string functions that are definable by an interpretation using monadic second-order (MSO) logic, are exactly those realized by deterministic two-way finite-state transducers, i.e., finite-state automata with a two-way input tape and a one-way output tape. Consequently, the equivalence of two mso definable string transductions is decidable. In the nondeterministic case however, MSO definable string transductions, i.e., binary relations on strings that are mso definable by an interpretation with parameters, are incomparable to those realized by nondeterministic two-way finite-state transducers. This is a motivation to look for another machine model, and we show that both classes of MSO definable string transductions are characterized in terms of Hennie machines, i.e., two-way finite-state transducers that are allowed to rewrite their input tape, but may visit each position of their input only a bounded number of times.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", generalterms = "Theory", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "B{\"u} chi; Elgot; Hennie machine; interpretation; monadic second-order logic; string transductions; Trakhtenbrot; two-way finite-state transducers", subject = "Theory of Computation --- Computation by Abstract Devices --- Models of Computation (F.1.1): {\bf Automata}; Theory of Computation --- Computation by Abstract Devices --- Models of Computation (F.1.1): {\bf Relations between models}; Theory of Computation --- Mathematical Logic and Formal Languages --- Mathematical Logic (F.4.1); Theory of Computation --- Mathematical Logic and Formal Languages --- Formal Languages (F.4.3)", } @Article{Antoniou:2001:RRD, author = "Grigoris Antoniou and David Billington and Guido Governatori and Michael J. Maher", title = "Representation results for defeasible logic", journal = j-TOCL, volume = "2", number = "2", pages = "255--287", year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jul 25 07:10:50 MDT 2001", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/articles/journals/tocl/2001-2-2/p255-antoniou/p255-antoniou.pdf; http://www.acm.org/pubs/citations/journals/tocl/2001-2-2/p255-antoniou/", abstract = "The importance of transformations and normal forms in logic programming, and generally in computer science, is well documented. This paper investigates transformations and normal forms in the context of Defeasible Logic, a simple but efficient formalism for nonmonotonic reasoning based on rules and priorities. The transformations described in this paper have two main benefits: on one hand they can be used as a theoretical tool that leads to a deeper understanding of the formalism, and on the other hand they have been used in the development of an efficient implementation of defeasible logic.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", generalterms = "Theory", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "defeasible logic; normal forms; transformations", subject = "Computing Methodologies --- Artificial Intelligence --- Knowledge Representation Formalisms and Methods (I.2.4); Theory of Computation --- Mathematical Logic and Formal Languages --- Mathematical Logic (F.4.1): {\bf Proof theory}", } @Article{Lukasiewicz:2001:PLP, author = "Thomas Lukasiewicz", title = "Probabilistic logic programming with conditional constraints", journal = j-TOCL, volume = "2", number = "3", pages = "289--339", year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jul 25 07:10:50 MDT 2001", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/citations/journals/tocl/2001-2-3/p289-lukasiewicz/", abstract = "We introduce a new approach to probabilistic logic programming in which probabilities are defined over a set of possible worlds. More precisely, classical program clauses are extended by a subinterval of [0,1] that describes a range for the conditional probability of the head of a clause given its body. We then analyze the complexity of selected probabilistic logic programming tasks. It turns out that probabilistic logic programming is computationally more complex than classical logic programming, More precisely, the tractability of special cases of classical logic programming generally does not carry over to the corresponding special cases of probabilistic logic programming. Moreover, we also draw a precise picture of the complexity of deciding and computing tight logical consequences in probabilistic reasoning with conditional constraints in general. We then present linear optimization techniques for deciding satisfiability and computing tight logical consequences of probabilistic logic programs. These techniques are efficient in the special case in which we have little relevant purely probabilistic knowledge. We finally show that probabilistic logic programming under certain syntactic and semantic restrictions is closely related to van Emden's quantitative deduction, and thus has computational properties similar to classical logic programming. Based on this result, we present an efficient approximation technique for probabilistic logic programming.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", generalterms = "Algorithms; Languages; Theory", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "computational complexity; conditional constraint; logic programming; many-valued logic; probabilistic logic; probabilistic logic programming; probabilistic reasoning; probability; quantitative deduction; uncertainty", subject = "Computing Methodologies --- Artificial Intelligence --- Deduction and Theorem Proving (I.2.3): {\bf Logic programming}; Computing Methodologies --- Artificial Intelligence --- Deduction and Theorem Proving (I.2.3): {\bf Uncertainty, ``fuzzy,'' and probabilistic reasoning}; Computing Methodologies --- Artificial Intelligence --- Knowledge Representation Formalisms and Methods (I.2.4)", } @Article{Egly:2001:PCR, author = "Uwe Egly and Hans Tompits", title = "Proof-complexity results for nonmonotonic reasoning", journal = j-TOCL, volume = "2", number = "3", pages = "340--387", year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jul 25 07:10:50 MDT 2001", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/citations/journals/tocl/2001-2-3/p340-egly/", abstract = "It is well-known that almost all nonmonotonic formalisms have a higher worst-case complexity than classical reasoning. In some sense, this observation denies one of the original motivations of nonmonotonic systems, which was the expectation that nonmonotonic rules should help to {\em speed-up\/} the reasoning process, and not make it more difficult. In this paper, we look at this issue from a proof-theoretical perspective. We consider analytic calculi for certain nonmonotonic logics and analyze to what extent the presence of nonmonotonic rules can simplify the search for proofs. In particular, we show that there are classes of first-order formulae which have only extremely long ``classical'' proofs, i.e., proofs without applications of nonmonotonic rules, but there are short proofs using nonmonotonic inferences. Hence,despite the increase of complexity in the worst case, there are instances where nonmonotonic reasoning can be much simpler than classical (cut-free) reasoning.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", generalterms = "Theory", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "circumscription; default logic; sequent calculi", subject = "Computing Methodologies --- Artificial Intelligence --- Deduction and Theorem Proving (I.2.3): {\bf Nonmonotonic reasoning and belief revision}; Theory of Computation --- Mathematical Logic and Formal Languages --- Mathematical Logic (F.4.1): {\bf Computational logic}; Theory of Computation --- Mathematical Logic and Formal Languages --- Mathematical Logic (F.4.1): {\bf Mechanical theorem proving}; Theory of Computation --- Mathematical Logic and Formal Languages --- Mathematical Logic (F.4.1): {\bf Proof theory}", } @Article{Alur:2001:PTL, author = "Rajeev Alur and Kousha Etessami and Salvatore {La Torre} and Doron Peled", title = "Parametric temporal logic for ``model measuring''", journal = j-TOCL, volume = "2", number = "3", pages = "388--407", year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jul 25 07:10:50 MDT 2001", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/citations/journals/tocl/2001-2-3/p388-alur/", abstract = "We extend the standard model checking paradigm of linear temporal logic, LTL, to a ``model measuring'' paradigm where one can obtain more quantitative information beyond a ``Yes/No'' answer. For this purpose, we define a {\em parametric temporal logic\/}, PLTL, which allows statements such as ``a request $p$ is followed in at most $x$ steps by a response $q$,'' where $x$ is a free variable. We show how one can, given a formula ***( {\em x 1 ...,xk\/} ) of PLTL and a system model {\em K\/} satisfies the property ***, but if so find valuations which satisfy various optimality criteria. In particular, we present algorithms for finding valuations which minimize (or maximize) the maximum (or minimum) of all parameters. Theses algorithms exhibit the same PSPACE complexity as LTL model checking. We show that our choice of syntax for PLTL lies at the threshold of decidability for parametric temporal logics, in that several natural extensions have undecidable ``model measuring'' problems.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", generalterms = "Theory; Verification", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "model checking; quantitative analysis; temporal logic", subject = "Theory of Computation --- Mathematical Logic and Formal Languages --- Mathematical Logic (F.4.1): {\bf Temporal logic}; Software --- Software Engineering --- Software/Program Verification (D.2.4): {\bf Model checking}; Theory of Computation --- Logics and Meanings of Programs --- Specifying and Verifying and Reasoning about Programs (F.3.1): {\bf Logics of programs}", } @Article{Kupferman:2001:WAA, author = "Orna Kupferman and Moshe Y. Vardi", title = "Weak alternating automata are not that weak", journal = j-TOCL, volume = "2", number = "3", pages = "408--429", year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jul 25 07:10:50 MDT 2001", bibsource = "http://www.acm.org/pubs/toc/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", URL = "http://www.acm.org/pubs/citations/journals/tocl/2001-2-3/p408-kupferman/", abstract = "Automata on infinite words are used for specification and verification of nonterminating programs. Different types of automata induce different levels of expressive power, of succinctness, and of complexity. {\em Alternating automata\/} have both existential and universal branching modes and are particularly suitable for specification of programs. In a {\em weak alternating automata\/} the state space is partitioned into partially ordered sets, and the automaton can proceed from a certain set only to smaller sets. Reasoning about weak alternating automata is easier than reasoning about alternating automata with no restricted structure. Known translations of alternating automata to weak alternating automata involve determinization, and therefore involve a double-exponential blow-up. In this paper we describe a quadratic translation, which circumvents the need for determinization, of B{\"u}chi and co-B{\"u}chi alternating automata to weak alternating automata. Beyond the independent interest of such a translation, it gives rise to a simple complementation algorithm for nondeterministic B{\"u}chi automata.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", generalterms = "Theory; Verification", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "complementation; weak alternating automata", subject = "Theory of Computation --- Computation by Abstract Devices --- Models of Computation (F.1.1): {\bf Automata}; Theory of Computation --- Computation by Abstract Devices --- Modes of Computation (F.1.2): {\bf Alternation and nondeterminism}; Theory of Computation --- Logics and Meanings of Programs --- Specifying and Verifying and Reasoning about Programs (F.3.1): {\bf Mechanical verification}", } @Article{Apt:2001:E, author = "Krzysztof R. Apt and Antonis C. Kakas and Fariba Sadri", title = "Editorial", journal = j-TOCL, volume = "2", number = "4", pages = "431--431", month = oct, year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Feb 19 15:32:34 MST 2002", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Reiter:2001:KBP, author = "Ray Reiter", title = "On knowledge-based programming with sensing in the situation calculus", journal = j-TOCL, volume = "2", number = "4", pages = "433--457", month = oct, year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Feb 19 15:32:35 MST 2002", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Lavrac:2001:ETA, author = "Nada Lavra{\v{c}} and Peter A. Flach", title = "An extended transformation approach to inductive logic programming", journal = j-TOCL, volume = "2", number = "4", pages = "458--494", month = oct, year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Feb 19 15:32:35 MST 2002", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{DeGiacomo:2001:IEG, author = "Giuseppe {De Giacomo} and Hector J. Levesque and Sebastian Sardi{\~n}a", title = "Incremental execution of guarded theories", journal = j-TOCL, volume = "2", number = "4", pages = "495--525", month = oct, year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Feb 19 15:32:35 MST 2002", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Lifschitz:2001:SEL, author = "Vladimir Lifschitz and David Pearce and Agust{\'\i}n Valverde", title = "Strongly equivalent logic programs", journal = j-TOCL, volume = "2", number = "4", pages = "526--541", month = oct, year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Feb 19 15:32:35 MST 2002", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Aiello:2001:VSP, author = "Luigia Carlucci Aiello and Fabio Massacci", title = "Verifying security protocols as planning in logic programming", journal = j-TOCL, volume = "2", number = "4", pages = "542--580", month = oct, year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Feb 19 15:32:35 MST 2002", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Sergot:2001:CTN, author = "Marek Sergot", title = "A computational theory of normative positions", journal = j-TOCL, volume = "2", number = "4", pages = "581--622", month = oct, year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Feb 19 15:32:35 MST 2002", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Denecker:2001:LPR, author = "Marc Denecker and Maurice Bruynooghe and Victor Marek", title = "Logic programming revisited: {Logic} programs as inductive definitions", journal = j-TOCL, volume = "2", number = "4", pages = "623--654", month = oct, year = "2001", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Feb 19 15:32:35 MST 2002", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Luttgen:2002:IBS, author = "Gerald L{\"u}ttgen and Michael Mendler", title = "The intuitionism behind {Statecharts} steps", journal = j-TOCL, volume = "3", number = "1", pages = "1--41", month = jan, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Feb 19 15:32:34 MST 2002", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Gottlob:2002:DLD, author = "Georg Gottlob and Erich Gr{\"a}del and Helmut Veith", title = "{Datalog LITE}: a deductive query language with linear time model checking", journal = j-TOCL, volume = "3", number = "1", pages = "42--79", month = jan, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Feb 19 15:32:34 MST 2002", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{McDowell:2002:RHO, author = "Raymond C. McDowell and Dale A. Miller", title = "Reasoning with higher-order abstract syntax in a logical framework", journal = j-TOCL, volume = "3", number = "1", pages = "80--136", month = jan, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Feb 19 15:32:34 MST 2002", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Asperti:2002:ILA, author = "Andrea Asperti and Luca Roversi", title = "Intuitionistic {Light Affine Logic}", journal = j-TOCL, volume = "3", number = "1", pages = "137--175", month = jan, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Feb 19 15:32:34 MST 2002", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Donini:2002:DLM, author = "Francesco M. Donini and Daniele Nardi and Riccardo Rosati", title = "Description logics of minimal knowledge and negation as failure", journal = j-TOCL, volume = "3", number = "2", pages = "177--225", month = apr, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:18 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bonatti:2002:SCP, author = "Piero Andrea Bonatti and Nicola Olivetti", title = "Sequent calculi for propositional nonmonotonic logics", journal = j-TOCL, volume = "3", number = "2", pages = "226--278", month = apr, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:18 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Tucker:2002:ACA, author = "J. V. Tucker and J. I. Zucker", title = "Abstract computability and algebraic specification", journal = j-TOCL, volume = "3", number = "2", pages = "279--333", month = apr, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:18 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Abadi:2002:E, author = "Mart{\'\i}n Abadi and Leonid Libkin and Frank Pfenning", title = "Editorial", journal = j-TOCL, volume = "3", number = "3", pages = "335--335", month = jul, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:19 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Grohe:2002:FOT, author = "Martin Grohe and Luc Segoufin", title = "On first-order topological queries", journal = j-TOCL, volume = "3", number = "3", pages = "336--358", month = jul, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:19 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Danos:2002:PGS, author = "Vincent Danos and Russell S. Harmer", title = "Probabilistic game semantics", journal = j-TOCL, volume = "3", number = "3", pages = "359--382", month = jul, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:19 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Aehlig:2002:SAN, author = "Klaus Aehlig and Helmut Schwichtenberg", title = "A syntactical analysis of non-size-increasing polynomial time computation", journal = j-TOCL, volume = "3", number = "3", pages = "383--401", month = jul, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:19 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Buss:2002:RBC, author = "Samuel R. Buss and Bruce M. Kapron", title = "Resource-bounded continuity and sequentiality for type-two functionals", journal = j-TOCL, volume = "3", number = "3", pages = "402--417", month = jul, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:19 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Gradel:2002:BFB, author = "Erich Gr{\"a}del and Colin Hirsch and Martin Otto", title = "Back and forth between guarded and modal logics", journal = j-TOCL, volume = "3", number = "3", pages = "418--463", month = jul, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:19 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bravetti:2002:DAW, author = "Mario Bravetti and Roberto Gorrieri", title = "Deciding and axiomatizing weak {ST} bisimulation for a process algebra with recursion and action refinement", journal = j-TOCL, volume = "3", number = "4", pages = "465--520", month = oct, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:19 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Givan:2002:PTC, author = "Robert Givan and David Mcallester", title = "Polynomial-time computation via local inference relations", journal = j-TOCL, volume = "3", number = "4", pages = "521--541", month = oct, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:19 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Kaminski:2002:RQA, author = "Michael Kaminski and Guy Rey", title = "Revisiting quantification in autoepistemic logic", journal = j-TOCL, volume = "3", number = "4", pages = "542--561", month = oct, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:19 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bono:2002:TIE, author = "Viviana Bono and Michele Bugliesi and Silvia Crafa", title = "Typed interpretations of extensible objects", journal = j-TOCL, volume = "3", number = "4", pages = "562--603", month = oct, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:19 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bryant:2002:BST, author = "Randal E. Bryant and Miroslav N. Velev", title = "{Boolean} satisfiability with transitivity constraints", journal = j-TOCL, volume = "3", number = "4", pages = "604--627", month = oct, year = "2002", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:19 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Wadler:2003:MEM, author = "Philip Wadler and Peter Thiemann", title = "The marriage of effects and monads", journal = j-TOCL, volume = "4", number = "1", pages = "1--32", month = jan, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:20 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Comon:2003:DCO, author = "Hubert Comon and Paliath Narendran and Robert Nieuwenhuis and Michael Rusinowitch", title = "Deciding the confluence of ordered term rewrite systems", journal = j-TOCL, volume = "4", number = "1", pages = "33--55", month = jan, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:20 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Harland:2003:RDB, author = "James Harland and David Pym", title = "Resource-distribution via {Boolean} constraints", journal = j-TOCL, volume = "4", number = "1", pages = "56--90", month = jan, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:20 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Lonc:2003:FPC, author = "Zbigniew Lonc and Miroslaw Truszczy{\'n}ski", title = "Fixed-parameter complexity of semantics for logic programs", journal = j-TOCL, volume = "4", number = "1", pages = "91--119", month = jan, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:20 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Dezani-Ciancaglini:2003:CCC, author = "M. Dezani-Ciancaglini and F. Honsell and F. Alessi", title = "A complete characterization of complete intersection-type preorders", journal = j-TOCL, volume = "4", number = "1", pages = "120--147", month = jan, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:20 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Angiulli:2003:CPM, author = "Fabrizio Angiulli and Rachel Ben-Eliyahu-Zohary and Giovambattista Ianni and Luigi Palopoli", title = "Computational properties of metaquerying problems", journal = j-TOCL, volume = "4", number = "2", pages = "149--180", month = apr, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:20 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bustan:2003:SBM, author = "Doron Bustan and Orna Grumberg", title = "Simulation-based minimization", journal = j-TOCL, volume = "4", number = "2", pages = "181--206", month = apr, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:20 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Mesnard:2003:PLT, author = "Fred Mesnard and Salvatore Ruggieri", title = "On proving left termination of constraint logic programs", journal = j-TOCL, volume = "4", number = "2", pages = "207--259", month = apr, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:20 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Kutz:2003:LMS, author = "Oliver Kutz and Frank Wolter and Holger Sturm and Nobu-Yuki Suzuki and Michael Zakharyaschev", title = "Logics of metric spaces", journal = j-TOCL, volume = "4", number = "2", pages = "260--294", month = apr, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:20 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Gradel:2003:LSI, author = "Erich Gr{\"a}del and Joseph Y. Halpern and Radha Jaghadeesan and Adolfo Piperno", title = "{LICS} 2001 special issue", journal = j-TOCL, volume = "4", number = "3", pages = "295--295", month = jul, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:21 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Adler:2003:LBF, author = "Micah Adler and Neil Immerman", title = "An $n!$ lower bound on formula size", journal = j-TOCL, volume = "4", number = "3", pages = "296--314", month = jul, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:21 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Alon:2003:TXV, author = "Noga Alon and Tova Milo and Frank Neven and Dan Suciu and Victor Vianu", title = "Typechecking {XML} views of relational databases", journal = j-TOCL, volume = "4", number = "3", pages = "315--354", month = jul, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:21 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Kozen:2003:SLP, author = "Dexter Kozen and Jerzy Tiuryn", title = "Substructural logic and partial correctness", journal = j-TOCL, volume = "4", number = "3", pages = "355--378", month = jul, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:21 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Salibra:2003:TIO, author = "Antonino Salibra", title = "Topological incompleteness and order incompleteness of the lambda calculus", journal = j-TOCL, volume = "4", number = "3", pages = "379--401", month = jul, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:21 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Avigad:2003:EDS, author = "Jeremy Avigad", title = "Eliminating definitions and {Skolem} functions in first-order logic", journal = j-TOCL, volume = "4", number = "3", pages = "402--415", month = jul, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Aug 7 10:03:21 MDT 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Shen:2003:DAC, author = "Yi-Dong Shen and Jia-Huai You and Li-Yan Yuan and Samuel S. P. Shen and Qiang Yang", title = "A dynamic approach to characterizing termination of general logic programs", journal = j-TOCL, volume = "4", number = "4", pages = "417--430", month = oct, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Oct 31 06:01:15 MST 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Libkin:2003:VIF, author = "Leonid Libkin", title = "Variable independence for first-order definable constraints", journal = j-TOCL, volume = "4", number = "4", pages = "431--451", month = oct, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Oct 31 06:01:15 MST 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bryans:2003:MCS, author = "Jeremy Bryans and Howard Bowman and John Derrick", title = "Model checking stochastic automata", journal = j-TOCL, volume = "4", number = "4", pages = "452--492", month = oct, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Oct 31 06:01:15 MST 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Momigliano:2003:HOP, author = "Alberto Momigliano and Frank Pfenning", title = "Higher-order pattern complement and the strict {$\lambda$}-calculus", journal = j-TOCL, volume = "4", number = "4", pages = "493--529", month = oct, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Oct 31 06:01:15 MST 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Buneman:2003:IBP, author = "Peter Buneman and Wenfei Fan and Scott Weinstein", title = "Interaction between path and type constraints", journal = j-TOCL, volume = "4", number = "4", pages = "530--577", month = oct, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Oct 31 06:01:15 MST 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Blass:2003:ASM, author = "Andreas Blass and Yuri Gurevich", title = "Abstract state machines capture parallel algorithms", journal = j-TOCL, volume = "4", number = "4", pages = "578--651", month = oct, year = "2003", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Oct 31 06:01:15 MST 2003", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Alur:2004:DGG, author = "Rajeev Alur and Salvatore {La Torre}", title = "Deterministic generators and games for {Ltl} fragments", journal = j-TOCL, volume = "5", number = "1", pages = "1--25", month = jan, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Sun Jan 11 10:23:00 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bloom:2004:PFD, author = "Bard Bloom and Wan Fokkink and Rob J. {Van Glabbeek}", title = "Precongruence formats for decorated trace semantics", journal = j-TOCL, volume = "5", number = "1", pages = "26--78", month = jan, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Sun Jan 11 10:23:00 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{DeNicola:2004:MLM, author = "Rocco {De Nicola} and Michele Loreti", title = "A modal logic for mobile agents", journal = j-TOCL, volume = "5", number = "1", pages = "79--128", month = jan, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Sun Jan 11 10:23:00 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Brass:2004:SLP, author = "Stefan Brass and J{\"u}rgen Dix and Teodor C. Przymusinski", title = "Super logic programs", journal = j-TOCL, volume = "5", number = "1", pages = "129--176", month = jan, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Sun Jan 11 10:23:00 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Abdennadher:2004:AGR, author = "Slim Abdennadher and Christophe Rigotti", title = "Automatic generation of rule-based constraint solvers over finite domains", journal = j-TOCL, volume = "5", number = "2", pages = "177--205", month = apr, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:48 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Eiter:2004:LPA, author = "Thomas Eiter and Wolfgang Faber and Nicola Leone and Gerald Pfeifer and Axel Polleres", title = "A logic programming approach to knowledge-state planning: {Semantics} and complexity", journal = j-TOCL, volume = "5", number = "2", pages = "206--263", month = apr, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:48 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Ratschan:2004:CAS, author = "Stefan Ratschan", title = "Convergent approximate solving of first-order constraints by approximate quantifiers", journal = j-TOCL, volume = "5", number = "2", pages = "264--281", month = apr, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:48 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Dawar:2004:IFP, author = "Anuj Dawar and Erich Gr{\"a}del and Stephan Kreutzer", title = "Inflationary fixed points in modal logic", journal = j-TOCL, volume = "5", number = "2", pages = "282--315", month = apr, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:48 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Subramani:2004:OLT, author = "K. Subramani", title = "Optimal length tree-like resolution refutations for {2SAT} formulas", journal = j-TOCL, volume = "5", number = "2", pages = "316--320", month = apr, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:48 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Godoy:2004:CTR, author = "Guillem Godoy and Robert Nieuwenhuis and Ashish Tiwari", title = "Classes of term rewrite systems with polynomial confluence problems", journal = j-TOCL, volume = "5", number = "2", pages = "321--331", month = apr, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:48 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Ignjatovic:2004:SAL, author = "Aleksandar Ignjatovic and Arun Sharma", title = "Some applications of logic to feasibility in higher types", journal = j-TOCL, volume = "5", number = "2", pages = "332--350", month = apr, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:48 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Michel:2004:DBI, author = "Laurent Michel and Pascal {Van Hentenryck}", title = "A decomposition-based implementation of search strategies", journal = j-TOCL, volume = "5", number = "2", pages = "351--383", month = apr, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:48 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Mielniczuk:2004:BTF, author = "Pawel Mielniczuk", title = "Basic theory of feature trees", journal = j-TOCL, volume = "5", number = "3", pages = "385--402", month = jul, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:49 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Neven:2004:FSM, author = "Frank Neven and Thomas Schwentick and Victor Vianu", title = "Finite state machines for strings over infinite alphabets", journal = j-TOCL, volume = "5", number = "3", pages = "403--435", month = jul, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:49 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bernardo:2004:SSR, author = "Marco Bernardo", title = "Symbolic semantic rules for producing compact {STGLAs} from value passing process descriptions", journal = j-TOCL, volume = "5", number = "3", pages = "436--469", month = jul, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:49 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bossi:2004:TSM, author = "Annalisa Bossi and Sandro Etalle and Sabina Rossi and Jan-Georg Smaus", title = "Termination of simply moded logic programs with dynamic scheduling", journal = j-TOCL, volume = "5", number = "3", pages = "470--507", month = jul, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:49 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Loyer:2004:HBS, author = "Yann Loyer and Nicolas Spyratos and Daniel Stamate", title = "Hypothesis-based semantics of logic programs in multivalued logics", journal = j-TOCL, volume = "5", number = "3", pages = "508--527", month = jul, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:49 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Basin:2004:RMF, author = "David Basin and Manuel Clavel and Jos{\'e} Meseguer", title = "Reflective metalogical frameworks", journal = j-TOCL, volume = "5", number = "3", pages = "528--576", month = jul, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:49 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Griffioen:2004:TNS, author = "David Griffioen and Frits Vaandrager", title = "A theory of normed simulations", journal = j-TOCL, volume = "5", number = "4", pages = "577--610", month = oct, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:49 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Tucker:2004:AVC, author = "J. V. Tucker and J. I. Zucker", title = "Abstract versus concrete computation on metric partial algebras", journal = j-TOCL, volume = "5", number = "4", pages = "611--668", month = oct, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:49 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Lutz:2004:NTC, author = "Carsten Lutz", title = "{NEXP TIME}-complete description logics with concrete domains", journal = j-TOCL, volume = "5", number = "4", pages = "669--705", month = oct, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:49 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{DeBoer:2004:PCT, author = "Frank S. {De Boer} and Maurizio Gabbrielli and Maria Chiara Meo", title = "Proving correctness of timed concurrent constraint programs", journal = j-TOCL, volume = "5", number = "4", pages = "706--731", month = oct, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:49 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Benhamou:2004:ICS, author = "Fr{\'e}d{\'e}ric Benhamou and Fr{\'e}d{\'e}ric Goualard and {\'E}ric Langu{\'e}nou and Marc Christie", title = "Interval constraint solving for camera control and motion planning", journal = j-TOCL, volume = "5", number = "4", pages = "732--767", month = oct, year = "2004", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Nov 4 07:59:49 MST 2004", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Henzinger:2005:CST, author = "Thomas A. Henzinger and Rupak Majumdar and Jean-Fran{\c{c}}ois Raskin", title = "A classification of symbolic transition systems", journal = j-TOCL, volume = "6", number = "1", pages = "1--32", month = jan, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Apr 12 06:59:19 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Giacobazzi:2005:MAD, author = "Roberto Giacobazzi and Francesco Ranzato and Francesca Scozzari", title = "Making abstract domains condensing", journal = j-TOCL, volume = "6", number = "1", pages = "33--60", month = jan, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Apr 12 06:59:19 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Harper:2005:ECF, author = "Robert Harper and Frank Pfenning", title = "On equivalence and canonical forms in the {LF} type theory", journal = j-TOCL, volume = "6", number = "1", pages = "61--101", month = jan, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Apr 12 06:59:19 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Verma:2005:NDT, author = "Rakesh Verma and Ara Hayrapetyan", title = "A new decidability technique for ground term rewriting systems with applications", journal = j-TOCL, volume = "6", number = "1", pages = "102--123", month = jan, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Apr 12 06:59:19 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Liau:2005:MLF, author = "Churn-Jung Liau", title = "A modal logic framework for multi-agent belief fusion", journal = j-TOCL, volume = "6", number = "1", pages = "124--174", month = jan, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Apr 12 06:59:19 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Hesselink:2005:EVP, author = "Wim H. Hesselink", title = "Eternity variables to prove simulation of specifications", journal = j-TOCL, volume = "6", number = "1", pages = "175--201", month = jan, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Apr 12 06:59:19 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Sakama:2005:IAS, author = "Chiaki Sakama", title = "Induction from answer sets in nonmonotonic logic programs", journal = j-TOCL, volume = "6", number = "2", pages = "203--231", month = apr, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Apr 12 06:59:19 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Cadoli:2005:CPN, author = "Marco Cadoli and Thomas Eiter and Georg Gottlob", title = "Complexity of propositional nested circumscription and nested abnormality theories", journal = j-TOCL, volume = "6", number = "2", pages = "232--272", month = apr, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Apr 12 06:59:19 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Kupferman:2005:LTB, author = "Orna Kupferman and Moshe Y. Vardi", title = "From linear time to branching time", journal = j-TOCL, volume = "6", number = "2", pages = "273--294", month = apr, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Apr 12 06:59:19 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Wang:2005:CCW, author = "Kewen Wang and Lizhu Zhou", title = "Comparisons and computation of well-founded semantics for disjunctive logic programs", journal = j-TOCL, volume = "6", number = "2", pages = "295--327", month = apr, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Apr 12 06:59:19 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Cohen:2005:EAA, author = "Sara Cohen and Yehoshua Sagiv and Werner Nutt", title = "Equivalences among aggregate queries with negation", journal = j-TOCL, volume = "6", number = "2", pages = "328--360", month = apr, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Apr 12 06:59:19 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Korovin:2005:KBC, author = "Konstantin Korovin and Andrei Voronkov", title = "{Knuth--Bendix} constraint solving is {NP}-complete", journal = j-TOCL, volume = "6", number = "2", pages = "361--388", month = apr, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Apr 12 06:59:19 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Eiter:2005:RAE, author = "Thomas Eiter and Michael Fink and Giuliana Sabbatini and Hans Tompits", title = "Reasoning about evolving nonmonotonic knowledge bases", journal = j-TOCL, volume = "6", number = "2", pages = "389--440", month = apr, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Apr 12 06:59:19 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Rondogiannis:2005:MMS, author = "Panos Rondogiannis and William W. Wadge", title = "Minimum model semantics for logic programs with negation-as-failure", journal = j-TOCL, volume = "6", number = "2", pages = "441--467", month = apr, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Apr 12 06:59:19 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Aehlig:2005:EFS, author = "Klaus Aehlig and Jan Johannsen", title = "An elementary fragment of second-order lambda calculus", journal = j-TOCL, volume = "6", number = "2", pages = "468--480", month = apr, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Apr 12 06:59:19 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Afrati:2005:DPT, author = "Foto Afrati and Stavros Cosmadakis and Eug{\'e}nie Foustoucos", title = "{Datalog} programs and their persistency numbers", journal = j-TOCL, volume = "6", number = "3", pages = "481--518", month = jul, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Jul 7 12:34:03 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Ferrari:2005:CDP, author = "Mauro Ferrari and Camillo Fiorentini and Guido Fiorino", title = "On the complexity of the disjunction property in intuitionistic and modal logics", journal = j-TOCL, volume = "6", number = "3", pages = "519--538", month = jul, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Jul 7 12:34:03 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Stone:2005:DMG, author = "Matthew Stone", title = "Disjunction and modular goal-directed proof search", journal = j-TOCL, volume = "6", number = "3", pages = "539--577", month = jul, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Jul 7 12:34:03 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Metcalfe:2005:SHC, author = "George Metcalfe and Nicola Olivetti and Dov Gabbay", title = "Sequent and hypersequent calculi for abelian and {{\L}ukasiewicz} logics", journal = j-TOCL, volume = "6", number = "3", pages = "578--613", month = jul, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Jul 7 12:34:03 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Boigelot:2005:EDP, author = "Bernard Boigelot and S{\'e}bastien Jodogne and Pierre Wolper", title = "An effective decision procedure for linear arithmetic over the integers and reals", journal = j-TOCL, volume = "6", number = "3", pages = "614--633", month = jul, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Jul 7 12:34:03 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Schweikardt:2005:AFO, author = "Nicole Schweikardt", title = "Arithmetic, first-order logic, and counting quantifiers", journal = j-TOCL, volume = "6", number = "3", pages = "634--671", month = jul, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Jul 7 12:34:03 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Apt:2005:E, author = "Krzysztof R. Apt", title = "Editorial", journal = j-TOCL, volume = "6", number = "4", pages = "673--673", month = oct, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Oct 17 07:03:25 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Kolaitis:2005:LSI, author = "Phokion G. Kolaitis", title = "{LICS 2003} special issue", journal = j-TOCL, volume = "6", number = "4", pages = "674--674", month = oct, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Oct 17 07:03:25 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Khoussainov:2005:ALO, author = "Bakhadyr Khoussainov and Sasha Rubin and Frank Stephan", title = "Automatic linear orders and trees", journal = j-TOCL, volume = "6", number = "4", pages = "675--700", month = oct, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Oct 17 07:03:25 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Murawski:2005:AUP, author = "Andrzej S. Murawski", title = "About the undecidability of program equivalence in finitary languages with state", journal = j-TOCL, volume = "6", number = "4", pages = "701--726", month = oct, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Oct 17 07:03:25 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Lynch:2005:CLR, author = "James F. Lynch", title = "Convergence law for random graphs with specified degree sequence", journal = j-TOCL, volume = "6", number = "4", pages = "727--748", month = oct, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Oct 17 07:03:25 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Miller:2005:PTG, author = "Dale Miller and Alwen Tiu", title = "A proof theory for generic judgments", journal = j-TOCL, volume = "6", number = "4", pages = "749--783", month = oct, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Oct 17 07:03:25 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Hughes:2005:PNU, author = "Dominic J. D. Hughes and Rob J. {Van Glabbeek}", title = "Proof nets for unit-free multiplicative-additive linear logic", journal = j-TOCL, volume = "6", number = "4", pages = "784--842", month = oct, year = "2005", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Oct 17 07:03:25 MDT 2005", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Janhunen:2006:UPD, author = "Tomi Janhunen and Ilkka Niemel{\"a} and Dietmar Seipel and Patrik Simons and Jia-Huai You", title = "Unfolding partiality and disjunctions in stable model semantics", journal = j-TOCL, volume = "7", number = "1", pages = "1--37", month = jan, year = "2006", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Mar 9 05:54:01 MST 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{East:2006:PCB, author = "Deborah East and Miroslaw Truszczy{\'n}ski", title = "Predicate-calculus-based logics for modeling and solving search problems", journal = j-TOCL, volume = "7", number = "1", pages = "38--83", month = jan, year = "2006", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Mar 9 05:54:01 MST 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Liberatore:2006:CRD, author = "Paolo Liberatore", title = "Complexity results on {DPLL} and resolution", journal = j-TOCL, volume = "7", number = "1", pages = "84--107", month = jan, year = "2006", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Mar 9 05:54:01 MST 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Degtyarev:2006:MTR, author = "Anatoli Degtyarev and Michael Fisher and Boris Konev", title = "Monodic temporal resolution", journal = j-TOCL, volume = "7", number = "1", pages = "108--150", month = jan, year = "2006", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Mar 9 05:54:01 MST 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Dix:2006:HTP, author = "J{\"u}rgen Dix and Sarit Kraus and V. S. Subrahmanian", title = "Heterogeneous temporal probabilistic agents", journal = j-TOCL, volume = "7", number = "1", pages = "151--198", month = jan, year = "2006", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Mar 9 05:54:01 MST 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Impagliazzo:2006:CDF, author = "Russell Impagliazzo and Nathan Segerlind", title = "Constant-depth {Frege} systems with counting axioms polynomially simulate {Nullstellensatz} refutations", journal = j-TOCL, volume = "7", number = "2", pages = "199--218", month = apr, year = "2006", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu May 11 11:32:04 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Coppola:2006:OOR, author = "Paolo Coppola and Simone Martini", title = "Optimizing optimal reduction: a type inference algorithm for elementary affine logic", journal = j-TOCL, volume = "7", number = "2", pages = "219--260", month = apr, year = "2006", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu May 11 11:32:04 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Lifschitz:2006:WTM, author = "Vladimir Lifschitz and Alexander Razborov", title = "Why are there so many loop formulas?", journal = j-TOCL, volume = "7", number = "2", pages = "261--268", month = apr, year = "2006", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu May 11 11:32:04 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Dovier:2006:DRS, author = "Agostino Dovier and Andrea Formisano and Eugenio G. Omodeo", title = "Decidability results for sets with atoms", journal = j-TOCL, volume = "7", number = "2", pages = "269--301", month = apr, year = "2006", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu May 11 11:32:04 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Japaridze:2006:PCLa, author = "Giorgi Japaridze", title = "Propositional computability logic {I}", journal = j-TOCL, volume = "7", number = "2", pages = "302--330", month = apr, year = "2006", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu May 11 11:32:04 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Japaridze:2006:PCLb, author = "Giorgi Japaridze", title = "Propositional computability logic {II}", journal = j-TOCL, volume = "7", number = "2", pages = "331--362", month = apr, year = "2006", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu May 11 11:32:04 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Blass:2006:OIS, author = "Andreas Blass and Yuri Gurevich", title = "Ordinary interactive small-step algorithms, {I}", journal = j-TOCL, volume = "7", number = "2", pages = "363--419", month = apr, year = "2006", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu May 11 11:32:04 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Zhang:2006:LPB, author = "Yan Zhang", title = "Logic program-based updates", journal = j-TOCL, volume = "7", number = "3", pages = "421--472", month = jul, year = "2006", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1149114.1149115", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Oct 17 05:32:00 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Murawski:2006:FVM, author = "Andrzej S. Murawski and C.-H. Luke Ong", title = "Fast verification of {MLL} proof nets via {IMLL}", journal = j-TOCL, volume = "7", number = "3", pages = "473--498", month = jul, year = "2006", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1149114.1149116", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Oct 17 05:32:00 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Leone:2006:DSK, author = "Nicola Leone and Gerald Pfeifer and Wolfgang Faber and Thomas Eiter and Georg Gottlob and Simona Perri and Francesco Scarcello", title = "The {DLV} system for knowledge representation and reasoning", journal = j-TOCL, volume = "7", number = "3", pages = "499--562", month = jul, year = "2006", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1149114.1149117", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Oct 17 05:32:00 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bistarelli:2006:SCC, author = "Stefano Bistarelli and Ugo Montanari and Francesca Rossi", title = "Soft concurrent constraint programming", journal = j-TOCL, volume = "7", number = "3", pages = "563--589", month = jul, year = "2006", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1149114.1149118", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Oct 17 05:32:00 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Charlesworth:2006:CSC, author = "Arthur Charlesworth", title = "Comprehending software correctness implies comprehending an intelligence-related limitation", journal = j-TOCL, volume = "7", number = "3", pages = "590--612", month = jul, year = "2006", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1149114.1149119", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Oct 17 05:32:00 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Son:2006:DDK, author = "Tran Cao Son and Chitta Baral and Nam Tran and Sheila Mcilraith", title = "Domain-dependent knowledge in answer set planning", journal = j-TOCL, volume = "7", number = "4", pages = "613--657", month = oct, year = "2006", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1166109.1166110", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Oct 17 05:32:00 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Paulson:2006:DFE, author = "Lawrence C. Paulson", title = "Defining functions on equivalence classes", journal = j-TOCL, volume = "7", number = "4", pages = "658--675", month = oct, year = "2006", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1166109.1166111", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Oct 17 05:32:00 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Stone:2006:EES, author = "Christopher A. Stone and Robert Harper", title = "Extensional equivalence and singleton types", journal = j-TOCL, volume = "7", number = "4", pages = "676--722", month = oct, year = "2006", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1166109.1166112", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Oct 17 05:32:00 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Ratschan:2006:ESQ, author = "Stefan Ratschan", title = "Efficient solving of quantified inequality constraints over the real numbers", journal = j-TOCL, volume = "7", number = "4", pages = "723--748", month = oct, year = "2006", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1166109.1166113", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Oct 17 05:32:00 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Cook:2006:SRW, author = "Stephen Cook and Neil Thapen", title = "The strength of replacement in weak arithmetic", journal = j-TOCL, volume = "7", number = "4", pages = "749--764", month = oct, year = "2006", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1166109.1166114", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Oct 17 05:32:00 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Vennekens:2006:SOA, author = "Joost Vennekens and David Gilis and Marc Denecker", title = "Splitting an operator: {Algebraic} modularity results for logics with fixpoint semantics", journal = j-TOCL, volume = "7", number = "4", pages = "765--797", month = oct, year = "2006", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1166109.1166115", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Oct 17 05:32:00 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", note = "See erratum \cite{Vennekens:2007:ESO}.", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Desharnais:2006:KAD, author = "Jules Desharnais and Bernhard M{\"o}ller and Georg Struth", title = "{Kleene} algebra with domain", journal = j-TOCL, volume = "7", number = "4", pages = "798--833", month = oct, year = "2006", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1166109.1166116", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Oct 17 05:32:00 MDT 2006", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bonacina:2007:ACI, author = "Maria Paola Bonacina and Nachum Dershowitz", title = "Abstract canonical inference", journal = j-TOCL, volume = "8", number = "1", pages = "??--??", month = jan, year = "2007", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Sat Apr 14 09:26:09 MDT 2007", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "6", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Guglielmi:2007:SIS, author = "Alessio Guglielmi", title = "A system of interaction and structure", journal = j-TOCL, volume = "8", number = "1", pages = "??--??", month = jan, year = "2007", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Sat Apr 14 09:26:09 MDT 2007", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "1", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Liberatore:2007:CPA, author = "Paolo Liberatore and Marco Schaerf", title = "Compilability of propositional abduction", journal = j-TOCL, volume = "8", number = "1", pages = "??--??", month = jan, year = "2007", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Sat Apr 14 09:26:09 MDT 2007", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "2", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{McIver:2007:RQC, author = "Annabelle McIver and Carroll Morgan", title = "Results on the quantitative $\mu$-calculus $q{M}\mu$", journal = j-TOCL, volume = "8", number = "1", pages = "??--??", month = jan, year = "2007", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Sat Apr 14 09:26:09 MDT 2007", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "3", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Rabinovich:2007:CL, author = "Alexander Rabinovich", title = "On compositionality and its limitations", journal = j-TOCL, volume = "8", number = "1", pages = "??--??", month = jan, year = "2007", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Sat Apr 14 09:26:09 MDT 2007", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "4", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Vennekens:2007:ESO, author = "Joost Vennekens and David Gilis and Marc Denecker", title = "Erratum to splitting an operator: {Algebraic} modularity results for logics with fixpoint semantics", journal = j-TOCL, volume = "8", number = "1", pages = "??--??", month = jan, year = "2007", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Sat Apr 14 09:26:09 MDT 2007", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", note = "See \cite{Vennekens:2006:SOA}.", acknowledgement = ack-nhfb, articleno = "7", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Yorsh:2007:LCH, author = "Greta Yorsh and Thomas Reps and Mooly Sagiv and Reinhard Wilhelm", title = "Logical characterizations of heap abstractions", journal = j-TOCL, volume = "8", number = "1", pages = "??--??", month = jan, year = "2007", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Sat Apr 14 09:26:09 MDT 2007", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "5", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Benedikt:2007:LDQ, author = "Michael Benedikt and Leonid Libkin and Frank Neven", title = "Logical definability and query languages over ranked and unranked trees", journal = j-TOCL, volume = "8", number = "2", pages = "??--??", month = apr, year = "2007", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Sat Apr 14 09:26:10 MDT 2007", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "11", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Crary:2007:SCE, author = "Karl Crary", title = "Sound and complete elimination of singleton kinds", journal = j-TOCL, volume = "8", number = "2", pages = "??--??", month = apr, year = "2007", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Sat Apr 14 09:26:10 MDT 2007", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "8", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Hitchcock:2007:ACD, author = "John M. Hitchcock and Jack H. Lutz and Sebastiaan A. Terwijn", title = "The arithmetical complexity of dimension and randomness", journal = j-TOCL, volume = "8", number = "2", pages = "??--??", month = apr, year = "2007", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Sat Apr 14 09:26:10 MDT 2007", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "13", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Liberatore:2007:WFS, author = "Paolo Liberatore", title = "Where fail-safe default logics fail", journal = j-TOCL, volume = "8", number = "2", pages = "??--??", month = apr, year = "2007", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Sat Apr 14 09:26:10 MDT 2007", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "10", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Lin:2007:RCA, author = "Fangzhen Lin and Jia-Huai You", title = "Recycling computed answers in rewrite systems for abduction", journal = j-TOCL, volume = "8", number = "2", pages = "??--??", month = apr, year = "2007", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Sat Apr 14 09:26:10 MDT 2007", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "9", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Sofronie-Stokkermans:2007:UBD, author = "Viorica Sofronie-Stokkermans", title = "On unification for bounded distributive lattices", journal = j-TOCL, volume = "8", number = "2", pages = "??--??", month = apr, year = "2007", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Sat Apr 14 09:26:10 MDT 2007", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "12", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Pedicini:2007:PPE, author = "Marco Pedicini and Francesco Quaglia", title = "{PELCR}: {Parallel} environment for optimal lambda-calculus reduction", journal = j-TOCL, volume = "8", number = "3", pages = "14:1--14:??", month = jul, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1243996.1243997", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:15 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In this article we present the implementation of an environment supporting L{\'e}vy's optimal reduction for the $\lambda$-calculus on parallel (or distributed) computing systems. In a similar approach to Lamping's, we base our work on a graph reduction technique, known as directed virtual reduction, which is actually a restriction of Danos-Regnier virtual reduction.\par The environment, which we refer to as PELCR (parallel environment for optimal lambda-calculus reduction), relies on a strategy for directed virtual reduction, namely half combustion. While developing PELCR we adopted both a message aggregation technique, allowing reduction of the communication overhead, and a fair policy for distributing dynamically originated load among processors.\par We also present an experimental study demonstrating the ability of PELCR to definitely exploit the parallelism intrinsic to $\lambda$-terms while performing the reduction. We show how PELCR allows achieving up to 70--80\% of the ideal speedup on last generation multiprocessor computing systems. As a last note, the software modules have been developed with the C language and using a standard interface for message passing, that is, MPI, thus making PELCR itself a highly portable software package.", acknowledgement = ack-nhfb, articleno = "14", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "functional programming; geometry of interaction; linear logic; optimal reduction; parallel implementation; virtual reduction", } @Article{Blass:2007:OISa, author = "Andreas Blass and Yuri Gurevich", title = "Ordinary interactive small-step algorithms, {II}", journal = j-TOCL, volume = "8", number = "3", pages = "15:1--15:??", month = jul, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1243996.1243998", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:15 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "This is the second in a series of three articles extending the proof of the Abstract State Machine Thesis---that arbitrary algorithms are behaviorally equivalent to abstract state machines---to algorithms that can interact with their environments during a step, rather than only between steps. As in the first article of the series, we are concerned here with ordinary, small-step, interactive algorithms. This means that the algorithms:\par (1) proceed in discrete, global steps,\par (2) perform only a bounded amount of work in each step,\par (3) use only such information from the environment as can be regarded as answers to queries, and\par (4) never complete a step until all queries from that step have been answered.\par After reviewing the previous article's formal description of such algorithms and the definition of behavioral equivalence, we define ordinary, interactive, small-step abstract state machines (ASMs). Except for very minor modifications, these are the machines commonly used in the ASM literature. We define their semantics in the framework of ordinary algorithms and show that they satisfy the postulates for these algorithms.\par This material lays the groundwork for the final article in the series, in which we shall prove the Abstract State Machine thesis for ordinary, intractive, small-step algorithms: All such algorithms are equivalent to ASMs.", acknowledgement = ack-nhfb, articleno = "15", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "abstract state machines; equivalence of algorithms; interaction; postulates; sequential algorithms", } @Article{Blass:2007:OISb, author = "Andreas Blass and Yuri Gurevich", title = "Ordinary interactive small-step algorithms, {III}", journal = j-TOCL, volume = "8", number = "3", pages = "16:1--16:??", month = jul, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1243996.1243999", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:15 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "This is the third in a series of three articles extending the proof of the Abstract State Machine thesis---that arbitrary algorithms are behaviorally equivalent to abstract state machines---to algorithms that can interact with their environments during a step, rather than only between steps. As in the first two articles of the series, we are concerned here with ordinary, small-step, interactive algorithms. This means that the algorithms:\par (1) proceed in discrete, global steps,\par (2) perform only a bounded amount of work in each step,\par (3) use only such information from the environment as can be regarded as answers to queries, and\par (4) never complete a step until all queries from that step have been answered.\par After reviewing the previous articles' definitions of such algorithms, of behavioral equivalence, and of abstract state machines (ASMs), we prove the main result: Every ordinary, interactive, small-step algorithm is behaviorally equivalent to an ASM.\par We also discuss some possible variations of and additions to the ASM semantics.", acknowledgement = ack-nhfb, articleno = "16", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "abstract state machines; equivalence of algorithms; interaction; postulates; sequential algorithms", } @Article{Eiter:2007:SCC, author = "Thomas Eiter and Michael Fink and Stefan Woltran", title = "Semantical characterizations and complexity of equivalences in answer set programming", journal = j-TOCL, volume = "8", number = "3", pages = "17:1--17:??", month = jul, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1243996.1244000", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:15 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In recent research on nonmonotonic logic programming, repeatedly strong equivalence of logic programs $P$ and $Q$ has been considered, which holds if the programs $P \cup R$ and $Q \cup R$ have the same answer sets for any other program $R$. This property strengthens the equivalence of $P$ and $Q$ with respect to answer sets (which is the particular case for $R = {\emptyset}$), and has its applications in program optimization, verification, and modular logic programming. In this article, we consider more liberal notions of strong equivalence, in which the actual form of $R$ may be syntactically restricted. On the one hand, we consider uniform equivalence where $R$ is a set of facts, rather than a set of rules. This notion, which is well-known in the area of deductive databases, is particularly useful for assessing whether programs $P$ and $Q$ are equivalent as components of a logic program which is modularly structured. On the other hand, we consider relativized notions of equivalence where $R$ ranges over rules over a fixed alphabet, and thus generalize our results to relativized notions of strong and uniform equivalence. For all these notions, we consider disjunctive logic programs in the propositional (ground) case as well as some restricted classes, providing semantical characterizations and analyzing the computational complexity. Our results, which naturally extend to answer set semantics for programs with strong negation, complement the results on strong equivalence of logic programs and pave the way for optimizations in answer set solvers as a tool for input-based problem solving.", acknowledgement = ack-nhfb, articleno = "17", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "answer set semantics; computational complexity; program optimization; stable models; strong equivalence; uniform equivalence", } @Article{Arieli:2007:PRP, author = "Ofer Arieli", title = "Paraconsistent reasoning and preferential entailments by signed quantified {Boolean} formulae", journal = j-TOCL, volume = "8", number = "3", pages = "18:1--18:??", month = jul, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1243996.1244001", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:15 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We introduce a uniform approach of representing a variety of paraconsistent nonmonotonic formalisms by quantified Boolean formulae (QBFs) in the context of multiple-valued logics. We show that this framework provides a useful platform for capturing, in a simple and natural way, a wide range of methods for preferential reasoning. The outcome is a subtle approach to represent the underlying formalisms, which induces a straightforward way to compute the corresponding entailments: By incorporating off-the-shelf QBF solvers it is possible to simulate within our framework various kinds of preferential formalisms, among which are Priest's logic LPm of reasoning with minimal inconsistency, Batens' adaptive logic ACLuNs2, Besnard and Schaub's inference relation $|= n$, a variety of formula-preferential systems, some bilattice-based preferential relations (e.g., $= I_1$ and $|= I_2$), and consequence relations for reasoning with graded uncertainty, such as the four-valued logic $|= 4 c$.", acknowledgement = ack-nhfb, articleno = "18", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "paraconsistent and nonmonotonic reasoning; preferential semantics; quantified Boolean formulae", } @Article{Schmidt:2007:ATP, author = "Renate A. Schmidt and Ullrich Hustadt", title = "The axiomatic translation principle for modal logic", journal = j-TOCL, volume = "8", number = "4", pages = "19:1--19:??", month = aug, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1276920.1276921", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:36 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In this paper we present a translation principle, called the axiomatic translation, for reducing propositional modal logics with background theories, including triangular properties such as transitivity, Euclideanness and functionality, to decidable fragments of first-order logic. The goal of the axiomatic translation principle is to find simplified theories, which capture the inference problems in the original theory, but in a way that can be readily automated and is easier to deal with by existing (first-order) theorem provers than the standard translation. The principle of the axiomatic translation is conceptually very simple and can be almost completely automated. Soundness is automatic under reasonable assumptions, general decidability results can be stated and termination of ordered resolution is easily achieved. The non-trivial part of the approach is proving completeness. We prove results of completeness, decidability, model generation, the small model property and the interpolation property for a number of common and less common modal logics. We also present results of experiments with a number of first-order logic theorem provers which are very encouraging.", acknowledgement = ack-nhfb, articleno = "19", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "completeness; decidability; small model property; translation approach", } @Article{Laplante:2007:PAM, author = "Sophie Laplante and Richard Lassaigne and Fr{\'e}d{\'e}ric Magniez and Sylvain Peyronnet and Michel de Rougemont", title = "Probabilistic abstraction for model checking: an approach based on property testing", journal = j-TOCL, volume = "8", number = "4", pages = "20:1--20:??", month = aug, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1276920.1276922", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:36 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The goal of model checking is to verify the correctness of a given program, on all its inputs. The main obstacle, in many cases, is the intractably large size of the program's transition system. Property testing is a randomized method to verify whether some fixed property holds on individual inputs, by looking at a small random part of that input. We join the strengths of both approaches by introducing a new notion of probabilistic abstraction, and by extending the framework of model checking to include the use of these abstractions.\par Our abstractions map transition systems associated with large graphs to small transition systems associated with small random subgraphs. This reduces the original transition system to a family of small, even constant-size, transition systems. We prove that with high probability, ``sufficiently'' incorrect programs will be rejected ($\varepsilon$-robustness). We also prove that under a certain condition (exactness), correct programs will never be rejected (soundness).\par Our work applies to programs for graph properties such as bipartiteness, $k$-colorability, or any $\exists \forall$ first order graph properties. Our main contribution is to show how to apply the ideas of property testing to syntactic programs for such properties. We give a concrete example of an abstraction for a program for bipartiteness. Finally, we show that the relaxation of the test alone does not yield transition systems small enough to use the standard model checking method. More specifically, we prove, using methods from communication complexity, that the OBDD size remains exponential for approximate bipartiteness.", acknowledgement = ack-nhfb, articleno = "20", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "approximate verification; model checking; probabilistic abstraction; probabilistic verification; property testing", } @Article{Durand:2007:FOQ, author = "Arnaud Durand and Etienne Grandjean", title = "First-order queries on structures of bounded degree are computable with constant delay", journal = j-TOCL, volume = "8", number = "4", pages = "21:1--21:??", month = aug, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1276920.1276923", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:36 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "A relational structure is $d$-degree-bounded, for some integer $d$, if each element of the domain belongs to at most $d$ tuples. In this paper, we revisit the complexity of the evaluation problem of not necessarily Boolean first-order (FO) queries over $d$-degree-bounded structures. Query evaluation is considered here as a dynamical process. We prove that any FO query on $d$-degree-bounded structures belongs to the complexity class constant-Delay$_{\rm lin}$, that is, can be computed by an algorithm that has two separate parts: it has a precomputation step of time linear in the size of the structure and then, it outputs all solutions (i.e., tuples that satisfy the formula) one by one with a constant delay (i.e., depending on the size of the formula only) between each. Seen as a global process, this implies that queries on $d$-degree-bounded structures can be evaluated in total time $f(|\varphi|).(|S| + |\varphi(S)|)$ and space $g(|\varphi|).|S|$ where $S$ is the structure, $\varphi$ is the formula, $\varphi(S)$ is the result of the query and $f$, $g$ are some fixed functions. Among other things, our results generalize a result of Seese on the data complexity of the model-checking problem for $d$-degree-bounded structures. Besides, the originality of our approach compared to related results is that it does not rely on the Hanf's model-theoretic technique and is simple and informative since it essentially rests on a quantifier elimination method.", acknowledgement = ack-nhfb, articleno = "21", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "computational complexity; enumeration problems; first-order logic", } @Article{Olivetti:2007:SCT, author = "Nicola Olivetti and Gian Luca Pozzato and Camilla B. Schwind", title = "A sequent calculus and a theorem prover for standard conditional logics", journal = j-TOCL, volume = "8", number = "4", pages = "22:1--22:??", month = aug, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1276920.1276924", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:36 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In this paper we present a cut-free sequent calculus, called SeqS, for some standard conditional logics. The calculus uses labels and transition formulas and can be used to prove decidability and space complexity bounds for the respective logics. We also show that these calculi can be the base for uniform proof systems. Moreover, we present CondLean, a theorem prover in Prolog for these calculi.", acknowledgement = ack-nhfb, articleno = "22", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "analytic sequent calculi; automated deduction; conditional logics; labeled deductive systems; logic programming; proof theory", } @Article{Choi:2007:RPR, author = "C. W. Choi and J. H. M. Lee and P. J. Stuckey", title = "Removing propagation redundant constraints in redundant modeling", journal = j-TOCL, volume = "8", number = "4", pages = "23:1--23:??", month = aug, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1276920.1276925", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:36 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "A widely adopted approach to solving constraint satisfaction problems combines systematic tree search with various degrees of constraint propagation for pruning the search space. One common technique to improve the execution efficiency is to add redundant constraints, which are constraints logically implied by others in the problem model. However, some redundant constraints are propagation redundant and hence do not contribute additional propagation information to the constraint solver. Redundant constraints arise naturally in the process of redundant modeling where two models of the same problem are connected and combined through channeling constraints. In this paper, we give general theorems for proving propagation redundancy of one constraint with respect to channeling constraints and constraints in the other model. We illustrate, on problems from CSPlib (http://www.csplib.org), how detecting and removing propagation redundant constraints in redundant modeling can speed up search by several order of magnitudes.", acknowledgement = ack-nhfb, articleno = "23", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "constraint propagation; redundant constraints; redundant modeling", } @Article{Hung:2007:PIX, author = "Edward Hung and Lise Getoor and V. S. Subrahmanian", title = "Probabilistic interval {XML}", journal = j-TOCL, volume = "8", number = "4", pages = "24:1--24:??", month = aug, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1276920.1276926", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:36 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Interest in XML databases has been expanding rapidly over the last few years. In this paper, we study the problem of incorporating probabilistic information into XML databases. We propose the Probabilistic Interval XML ( PIXML for short) data model in this paper. Using this data model, users can express probabilistic information within XML markups. In addition, we provide two alternative formal model-theoretic semantics for PIXML data. The first semantics is a ``global'' semantics which is relatively intuitive, but is not directly amenable to computation. The second semantics is a ``local'' semantics which supports efficient computation. We prove several correspondence results between the two semantics. To our knowledge, this is the first formal model theoretic semantics for probabilistic interval XML. We then provide an operational semantics that may be used to compute answers to queries and that is correct for a large class of probabilistic instances.", acknowledgement = ack-nhfb, articleno = "24", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "semistructured databases; XML", } @Article{Shoham:2007:GBF, author = "Sharon Shoham and Orna Grumberg", title = "A game-based framework for {CTL} counterexamples and 3-valued abstraction-refinement", journal = j-TOCL, volume = "9", number = "1", pages = "1:1--1:??", month = dec, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1297658.1297659", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:49 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "This work exploits and extends the game-based framework of CTL model checking for counterexample and incremental abstraction-refinement. We define a game-based CTL model checking for abstract models over the 3-valued semantics, which can be used for verification as well as refutation. The model checking process of an abstract model may end with an indefinite result, in which case we suggest a new notion of refinement, which eliminates indefinite results of the model checking. This provides an iterative abstraction-refinement framework. This framework is enhanced by an incremental algorithm, where refinement is applied only where indefinite results exist and definite results from prior iterations are used within the model checking algorithm. We also define the notion of annotated counterexamples, which are sufficient and minimal counterexamples for full CTL. We present an algorithm that uses the game board of the model checking game to derive an annotated counterexample in case the examined system model refutes the checked formula.", acknowledgement = ack-nhfb, articleno = "1", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "3-valued semantics; abstraction-refinement; counterexamples; CTL; model checking games; temporal logic", } @Article{Avigad:2007:FVP, author = "Jeremy Avigad and Kevin Donnelly and David Gray and Paul Raff", title = "A formally verified proof of the prime number theorem", journal = j-TOCL, volume = "9", number = "1", pages = "2:1--2:23", month = dec, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1297658.1297660", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:49 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The prime number theorem, established by Hadamard and de la Vall{\'e}e Poussin independently in 1896, asserts that the density of primes in the positive integers is asymptotic to $1/\ln x$. Whereas their proofs made serious use of the methods of complex analysis, elementary proofs were provided by Selberg and Erd{\H{o}}s in 1948. We describe a formally verified version of Selberg's proof, obtained using the Isabelle proof assistant.", acknowledgement = ack-nhfb, articleno = "2", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "formal verification; prime number theorem", } @Article{VandenBussche:2007:PTI, author = "Jan {Van den Bussche} and Stijn Vansummeren", title = "Polymorphic type inference for the named nested relational calculus", journal = j-TOCL, volume = "9", number = "1", pages = "3:1--3:??", month = dec, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1297658.1297661", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:49 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The named nested relational calculus is the canonical query language for the complex object database model and is equipped with a natural static type system. Given an expression in the language, without type declarations for the input variables, there is the problem of whether there are any input type declarations under which the expression is well-typed. Moreover, if there are, then which are they, and what is the corresponding output type for each of these? This problem is solved by a logic-based approach, and the decision problem is shown to be NP-complete.", acknowledgement = ack-nhfb, articleno = "3", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "complexity; named nested relational calculus; typability; type inference", } @Article{Lahiri:2007:PAI, author = "Shuvendu K. Lahiri and Randal E. Bryant", title = "Predicate abstraction with indexed predicates", journal = j-TOCL, volume = "9", number = "1", pages = "4:1--4:??", month = dec, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1297658.1297662", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:49 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Predicate abstraction provides a powerful tool for verifying properties of infinite-state systems using a combination of a decision procedure for a subset of first-order logic and symbolic methods originally developed for finite-state model checking. We consider models containing first-order state variables, where the system state includes mutable functions and predicates. Such a model can describe systems containing arbitrarily large memories, buffers, and arrays of identical processes. We describe a form of predicate abstraction that constructs a formula over a set of universally quantified variables to describe invariant properties of the first-order state variables. We provide a formal justification of the soundness of our approach and describe how it has been used to verify several hardware and software designs, including a directory-based cache coherence protocol.", acknowledgement = ack-nhfb, articleno = "4", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "abstract interpretation; cache-coherence protocols; formal verification; infinite-state verification; invariant synthesis; predicate abstraction", } @Article{Baier:2007:VNP, author = "Christel Baier and Nathalie Bertrand and Philippe Schnoebelen", title = "Verifying nondeterministic probabilistic channel systems against $\omega$-regular linear-time properties", journal = j-TOCL, volume = "9", number = "1", pages = "5:1--5:??", month = dec, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1297658.1297663", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:49 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Lossy channel systems (LCS's) are systems of finite state processes that communicate via unreliable unbounded fifo channels. We introduce NPLCS's, a variant of LCS's where message losses have a probabilistic behavior while the component processes behave nondeterministically, and study the decidability of qualitative verification problems for $\omega$-regular linear-time properties.\par We show that---in contrast to finite-state Markov decision processes---the satisfaction relation for linear-time formulas depends on the type of schedulers that resolve the nondeterminism. While the qualitative model checking problem for the full class of history-dependent schedulers is undecidable, the same question for finite-memory schedulers can be solved algorithmically. Additionally, some special kinds of reachability, or recurrent reachability, qualitative properties yield decidable verification problems for the full class of schedulers, which---for this restricted class of problems---are as powerful as finite-memory schedulers, or even a subclass of them.", acknowledgement = ack-nhfb, articleno = "5", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "communication protocols; lossy channels; Markov decision processes; probabilistic models", } @Article{Biernacka:2007:CFE, author = "Ma{\l}gorzata Biernacka and Olivier Danvy", title = "A concrete framework for environment machines", journal = j-TOCL, volume = "9", number = "1", pages = "6:1--6:??", month = dec, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1297658.1297664", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:49 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We materialize the common understanding that calculi with explicit substitutions provide an intermediate step between an abstract specification of substitution in the lambda-calculus and its concrete implementations. To this end, we go back to Curien's original calculus of closures (an early calculus with explicit substitutions), we extend it minimally so that it can also express one-step reduction strategies, and we methodically derive a series of environment machines from the specification of two one-step reduction strategies for the lambda-calculus: normal order and applicative order. The derivation extends Danvy and Nielsen's refocusing-based construction of abstract machines with two new steps: one for coalescing two successive transitions into one, and the other for unfolding a closure into a term and an environment in the resulting abstract machine. The resulting environment machines include both the Krivine machine and the original version of Krivine's machine, Felleisen et al.'s CEK machine, and Leroy's Zinc abstract machine.", acknowledgement = ack-nhfb, articleno = "6", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "abstract machines; closures; derivation; explicit substitutions", } @Article{Angiulli:2007:ODL, author = "Fabrizio Angiulli and Gianluigi Greco and Luigi Palopoli", title = "Outlier detection by logic programming", journal = j-TOCL, volume = "9", number = "1", pages = "7:1--7:??", month = dec, year = "2007", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1297658.1297665", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:28:49 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The development of effective knowledge discovery techniques has become a very active research area in recent years due to the important impact it has had in several relevant application domains. One interesting task therein is that of singling out anomalous individuals from a given population, for example, to detect rare events in time-series analysis settings, or to identify objects whose behavior is deviant w.r.t. a codified standard set of rules. Such exceptional individuals are usually referred to as outliers in the literature.\par In this article, the concept of outlier is formally stated in the context of knowledge-based systems, by generalizing that originally proposed in Angiulli et al. [2003] in the context of default theories. The chosen formal framework here is that of logic programming, wherein potential applications of techniques for outlier detection are thoroughly discussed. The proposed formalization is a novel one and helps to shed light on the nature of outliers occurring in logic bases. Also the exploitation of minimality criteria in outlier detection is illustrated.\par The computational complexity of outlier detection problems arising in this novel setting is also thoroughly investigated and accounted for in the paper. Finally, rewriting algorithms are proposed that transform any outlier detection problem into an equivalent inference problem under stable model semantics, thereby making outlier computation effective and realizable on top of any stable model solver.", acknowledgement = ack-nhfb, articleno = "7", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "computational complexity; logic programming; nonmonotonic reasoning; outlier detection", } @Article{Ghilardi:2008:CCF, author = "Silvio Ghilardi and Enrica Nicolini and Daniele Zucchelli", title = "A comprehensive combination framework", journal = j-TOCL, volume = "9", number = "2", pages = "8:1--8:??", month = mar, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1342991.1342992", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:29:03 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We define a general notion of a fragment within higher-order type theory; a procedure for constraint satisfiability in combined fragments is outlined, following Nelson-Oppen schema. The procedure is in general only sound, but it becomes terminating and complete when the shared fragment enjoys suitable noetherianity conditions and admits an abstract version of a ``Keisler-Shelah-like'' isomorphism theorem. We show that this general decidability transfer result covers recent work on combination in first-order theories as well as in various intensional logics such as description, modal, and temporal logics.", acknowledgement = ack-nhfb, articleno = "8", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "combination; decision procedures; higher-order logic; modal and description logics; satisfiability modulo theory", } @Article{Sakama:2008:CAS, author = "Chiaki Sakama and Katsumi Inoue", title = "Coordination in answer set programming", journal = j-TOCL, volume = "9", number = "2", pages = "9:1--9:??", month = mar, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1342991.1342993", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:29:03 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "This article studies a semantics of multiple logic programs, and synthesizes a program having such a collective semantics. More precisely, the following two problems are considered: given two logic programs $P_1$ and $P_2$, which have the collections of answer sets ${\rm AS}(P_1)$ and ${\rm AS}(P_2)$, respectively; (i) find a program $Q$ which has the set of answer sets such that ${\rm AS}(Q) = {\rm AS}(P_1) \cup {\rm AS}(P_2)$; (ii) find a program R which has the set of answer sets such that ${\rm AS}(R) = {AS}(P_1) \cap {AS}(P_2)$. A program $Q$ satisfying the condition (i) is called generous coordination of $P_1$ and $P_2$; and $R$ satisfying (ii) is called rigorous coordination of $P_1$ and $P_2$. Generous coordination retains all of the answer sets of each program, but permits the introduction of additional answer sets of the other program. By contrast, rigorous coordination forces each program to give up some answer sets, but the result remains within the original answer sets for each program. Coordination provides a program that reflects the meaning of two or more programs. We provide methods for constructing these two types of coordination and address its application to logic-based multi-agent systems.", acknowledgement = ack-nhfb, articleno = "9", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "answer set programming; coordination; multiagent systems", } @Article{Lasota:2008:ATA, author = "Slawomir Lasota and Igor Walukiewicz", title = "Alternating timed automata", journal = j-TOCL, volume = "9", number = "2", pages = "10:1--10:??", month = mar, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1342991.1342994", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:29:03 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "A notion of alternating timed automata is proposed. It is shown that such automata with only one clock have decidable emptiness problem over finite words. This gives a new class of timed languages that is closed under boolean operations and which has an effective presentation. We prove that the complexity of the emptiness problem for alternating timed automata with one clock is nonprimitive recursive. The proof gives also the same lower bound for the universality problem for nondeterministic timed automata with one clock. We investigate extension of the model with epsilon-transitions and prove that emptiness is undecidable. Over infinite words, we show undecidability of the universality problem.", acknowledgement = ack-nhfb, articleno = "10", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "alternation; emptyness problem; timed automata", } @Article{Klaedtke:2008:BAS, author = "Felix Klaedtke", title = "Bounds on the automata size for {Presburger} arithmetic", journal = j-TOCL, volume = "9", number = "2", pages = "11:1--11:??", month = mar, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1342991.1342995", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:29:03 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Automata provide a decision procedure for Presburger arithmetic. However, until now only crude lower and upper bounds were known on the sizes of the automata produced by the automata-based approach for Presburger arithmetic. In this article, we give an upper bound on the number of states of the minimal deterministic automaton for a Presburger arithmetic formula. This bound depends on the length of the formula and the quantifiers occurring in it. We establish the upper bound by comparing the automata for Presburger arithmetic formulas with the formulas produced by a quantifier-elimination method. We show that our bound is tight, also for nondeterministic automata. Moreover, we provide automata constructions for atomic formulas and establish lower bounds for the automata for linear equations and inequations.", acknowledgement = ack-nhfb, articleno = "11", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "automata-based decision procedures; complexity; Presburger arithmetic; quantifier elimination", } @Article{Bruyere:2008:DPM, author = "V{\'e}ronique Bruy{\`e}re and Emmanuel Dall'olio and Jean-Fran{\c{c}}ois Raskin", title = "Durations and parametric model-checking in timed automata", journal = j-TOCL, volume = "9", number = "2", pages = "12:1--12:??", month = mar, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1342991.1342996", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:29:03 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We consider the problem of model-checking a parametric extension of the logic TCTL over timed automata and establish its decidability. Given a timed automaton, we show that the set of durations of runs starting from a region and ending in another region is definable in Presburger arithmetic (when the time domain is discrete) or in a real arithmetic (when the time domain is dense). Using this logical definition, we show that the parametric model-checking problem for the logic TCTL can be solved algorithmically; the proof of this result is simple. More generally, we are able to effectively characterize the values of the parameters that satisfy the parametric TCTL formula with respect to the given timed automaton.", acknowledgement = ack-nhfb, articleno = "12", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "model-checking; Presburger arithmetic; timed automata", } @Article{Geerts:2008:FOC, author = "Floris Geerts and Sofie Haesevoets and Bart Kuijpers", title = "First-order complete and computationally complete query languages for spatio-temporal databases", journal = j-TOCL, volume = "9", number = "2", pages = "13:1--13:??", month = mar, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1342991.1342997", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:29:03 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We address a fundamental question concerning spatio-temporal database systems: ``What are exactly spatio-temporal queries?'' We define spatio-temporal queries to be computable mappings that are also generic, meaning that the result of a query may only depend to a limited extent on the actual internal representation of the spatio-temporal data. Genericity is defined as invariance under groups of geometric transformations that preserve certain characteristics of spatio-temporal data (e.g., collinearity, distance, velocity, acceleration, {\ldots}). These groups depend on the notions that are relevant in particular spatio-temporal database applications. These transformations also have the distinctive property that they respect the monotone and unidirectional nature of time.\par We investigate different genericity classes with respect to the constraint database model for spatio-temporal databases and we identify sound and complete languages for the first-order and the computable queries in these genericity classes. We distinguish between genericity determined by time-invariant transformations, genericity notions concerning physical quantities and genericity determined by time-dependent transformations.", acknowledgement = ack-nhfb, articleno = "13", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "constraint databases; moving objects; query languages; spatial databases; spatio-temporal databases", } @Article{Denecker:2008:LNI, author = "Marc Denecker and Eugenia Ternovska", title = "A logic of nonmonotone inductive definitions", journal = j-TOCL, volume = "9", number = "2", pages = "14:1--14:??", month = mar, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1342991.1342998", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:29:03 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Well-known principles of induction include monotone induction and different sorts of nonmonotone induction such as inflationary induction, induction over well-founded sets and iterated induction. In this work, we define a logic formalizing induction over well-founded sets and monotone and iterated induction. Just as the principle of positive induction has been formalized in FO(LFP), and the principle of inflationary induction has been formalized in FO(IFP), this article formalizes the principle of iterated induction in a new logic for Nonmonotone Inductive Definitions (ID-logic). The semantics of the logic is strongly influenced by the well-founded semantics of logic programming.\par This article discusses the formalisation of different forms of (non-)monotone induction by the well-founded semantics and illustrates the use of the logic for formalizing mathematical and common-sense knowledge. To model different types of induction found in mathematics, we define several subclasses of definitions, and show that they are correctly formalized by the well-founded semantics. We also present translations into classical first or second order logic. We develop modularity and totality results and demonstrate their use to analyze and simplify complex definitions. We illustrate the use of the logic for temporal reasoning. The logic formally extends Logic Programming, Abductive Logic Programming and Datalog, and thus formalizes the view on these formalisms as logics of (generalized) inductive definitions.", acknowledgement = ack-nhfb, articleno = "14", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "classical logic; inductive definitions; logic programming", } @Article{Dovier:2008:UAC, author = "Agostino Dovier and Carla Piazza and Gianfranco Rossi", title = "A uniform approach to constraint-solving for lists, multisets, compact lists, and sets", journal = j-TOCL, volume = "9", number = "3", pages = "15:1--15:??", month = jun, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1352582.1352583", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:29:17 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Lists, multisets, and sets are well-known data structures whose usefulness is widely recognized in various areas of computer science. They have been analyzed from an axiomatic point of view with a parametric approach in Dovier et al. [1998], where the relevant unification algorithms have been developed. In this article, we extend these results considering more general constraints, namely, equality and membership constraints and their negative counterparts.", acknowledgement = ack-nhfb, articleno = "15", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "compact lists; lists; membership and equality constraints; multisets; sets", } @Article{Crary:2008:FCC, author = "Karl Crary and Susmit Sarkar", title = "Foundational certified code in the {Twelf} metalogical framework", journal = j-TOCL, volume = "9", number = "3", pages = "16:1--16:??", month = jun, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1352582.1352584", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:29:17 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Foundational certified code systems seek to prove untrusted programs to be safe relative to safety policies given in terms of actual machine architectures, thereby improving the systems' flexibility and extensibility. Using the Twelf metalogical framework, we have constructed a safety policy for the IA-32 architecture with a trusted runtime library. The safety policy is based on a formalized operational semantics. We have also developed a complete, foundational proof that a fully expressive typed assembly language satisfies that safety policy.", acknowledgement = ack-nhfb, articleno = "16", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "foundational certified code; logic programming; metalogic", } @Article{Genaim:2008:INS, author = "Samir Genaim and Andy King", title = "Inferring non-suspension conditions for logic programs with dynamic scheduling", journal = j-TOCL, volume = "9", number = "3", pages = "17:1--17:??", month = jun, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1352582.1352585", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:29:17 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "A logic program consists of a logic component and a control component. The former is a specification in predicate logic whereas the latter defines the order of subgoal selection. The order of subgoal selection is often controlled with delay declarations that specify that a subgoal is to suspend until some condition on its arguments is satisfied. Reasoning about delay declarations is notoriously difficult for the programmer and it is not unusual for a program and a goal to reduce to a state that contains a subgoal that suspends indefinitely. Suspending subgoals are usually unintended and often indicate an error in the logic or the control. A number of abstract interpretation schemes have therefore been proposed for checking that a given program and goal cannot reduce to such a state. This article considers a reversal of this problem, advocating an analysis that for a given program infers a class of goals that do not lead to suspension. This article shows that this more general approach can have computational, implementational and user-interface advantages. In terms of user-interface, this approach leads to a lightweight point-and-click mode of operation in which, after directing the analyser at a file, the user merely has to inspect the results inferred by the analysis. In terms of implementation, the analysis can be straightforwardly realized as two simple fixpoint computations. In terms of computation, by modeling $n!$ different schedulings of $n$ subgoals with a single Boolean function, it is possible to reason about the suspension behavior of large programs. In particular, the analysis is fast enough to be applied repeatedly within the program development cycle. The article also demonstrates that the method is precise enough to locate bugs in existing programs.", acknowledgement = ack-nhfb, articleno = "17", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "abstract interpretation; concurrency; debugging; logic programming", } @Article{Blass:2008:PTW, author = "Andreas Blass and Yuri Gurevich", title = "Program termination and well partial orderings", journal = j-TOCL, volume = "9", number = "3", pages = "18:1--18:??", month = jun, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1352582.1352586", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:29:17 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The following known observation is useful in establishing program termination: if a transitive relation $R$ is covered by finitely many well-founded relations $U_1, \ldots, U_n$ then $R$ is well-founded. A question arises how to bound the ordinal height $|R|$ of the relation $R$ in terms of the ordinals $\alpha_i = |U_i|$. We introduce the notion of the stature $||P||$ of a well partial ordering $P$ and show that $|R| \leq ||\alpha_1 \times \cdots \times \alpha_n||$ and that this bound is tight. The notion of stature is of considerable independent interest. We define $||P||$ as the ordinal height of the forest of nonempty bad sequences of $P$, but it has many other natural and equivalent definitions. In particular, $||P||$ is the supremum, and in fact the maximum, of the lengths of linearizations of $P$. And $||\alpha_1 \times \cdots \times \alpha_n ||$ is equal to the natural product $\alpha_1 \otimes \ldots \otimes \alpha_n$.", acknowledgement = ack-nhfb, articleno = "18", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "covering observation; game criterion; program termination; well partial orderings", } @Article{Blass:2008:ASM, author = "Andreas Blass and Yuri Gurevich", title = "Abstract state machines capture parallel algorithms: {Correction} and extension", journal = j-TOCL, volume = "9", number = "3", pages = "19:1--19:??", month = jun, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1352582.1352587", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:29:17 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We consider parallel algorithms working in sequential global time, for example, circuits or parallel random access machines (PRAMs). Parallel abstract state machines (parallel ASMs) are such parallel algorithms, and the parallel ASM thesis asserts that every parallel algorithm is behaviorally equivalent to a parallel ASM. In an earlier article, we axiomatized parallel algorithms, proved the ASM thesis, and proved that every parallel ASM satisfies the axioms. It turned out that we were too timid in formulating the axioms; they did not allow a parallel algorithm to create components on the fly. This restriction did not hinder us from proving that the usual parallel models, like circuits or PRAMs or even alternating Turing machines, satisfy the postulates. But it resulted in an error in our attempt to prove that parallel ASMs always satisfy the postulates. To correct the error, we liberalize our axioms and allow on-the-fly creation of new parallel components. We believe that the improved axioms accurately express what parallel algorithms ought to be. We prove the parallel thesis for the new, corrected notion of parallel algorithms, and we check that parallel ASMs satisfy the new axioms.", acknowledgement = ack-nhfb, articleno = "19", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "abstract state machine; ASM thesis; parallel algorithm; parallel programming; postulates for parallel computation", } @Article{Chockler:2008:WCS, author = "Hana Chockler and Joseph Y. Halpern and Orna Kupferman", title = "What causes a system to satisfy a specification?", journal = j-TOCL, volume = "9", number = "3", pages = "20:1--20:??", month = jun, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1352582.1352588", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:29:17 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", note = "See erratum \cite{Chockler:2010:EWC}.", abstract = "Even when a system is proven to be correct with respect to a specification, there is still a question of how complete the specification is, and whether it really covers all the behaviors of the system. Coverage metrics attempt to check which parts of a system are actually relevant for the verification process to succeed. Recent work on coverage in model checking suggests several coverage metrics and algorithms for finding parts of the system that are not covered by the specification. The work has already proven to be effective in practice, detecting design errors that escape early verification efforts in industrial settings. In this article, we relate a formal definition of causality given by Halpern and Pearl to coverage. We show that it gives significant insight into unresolved issues regarding the definition of coverage and leads to potentially useful extensions of coverage. In particular, we introduce the notion of responsibility, which assigns to components of a system a quantitative measure of their relevance to the satisfaction of the specification.", acknowledgement = ack-nhfb, articleno = "20", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "causality; coverage metrics; model checking; responsibility", } @Article{Bova:2008:PSH, author = "Simone Bova and Franco Montagna", title = "Proof search in {H{\'a}jek}'s basic logic", journal = j-TOCL, volume = "9", number = "3", pages = "21:1--21:??", month = jun, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1352582.1352589", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:29:17 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We introduce a proof system for H{\'a}jek's logic BL based on a relational hypersequents framework. We prove that the rules of our logical calculus, called RHBL, are sound and invertible with respect to any valuation of BL into a suitable algebra, called $(\omega)[0,1]$. Refining the notion of reduction tree that arises naturally from RHBL, we obtain a decision algorithm for BL provability whose running time upper bound is $2^O(n)$, where $n$ is the number of connectives of the input formula. Moreover, if a formula is unprovable, we exploit the constructiveness of a polynomial time algorithm for leaves validity for providing a procedure to build countermodels in $(\omega)[0, 1]$. Finally, since the size of the reduction tree branches is $O(n^3)$, we can describe a polynomial time verification algorithm for BL unprovability.", acknowledgement = ack-nhfb, articleno = "21", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "automated deduction; countermodel building; fuzzy logic", } @Article{Calvanese:2008:CQC, author = "Diego Calvanese and Giuseppe {De Giacomo} and Maurizio Lenzerini", title = "Conjunctive query containment and answering under description logic constraints", journal = j-TOCL, volume = "9", number = "3", pages = "22:1--22:??", month = jun, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1352582.1352590", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:29:17 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Query containment and query answering are two important computational tasks in databases. While query answering amounts to computing the result of a query over a database, query containment is the problem of checking whether, for every database, the result of one query is a subset of the result of another query.\par In this article, we deal with unions of conjunctive queries, and we address query containment and query answering under description logic constraints. Every such constraint is essentially an inclusion dependency between concepts and relations, and their expressive power is due to the possibility of using complex expressions in the specification of the dependencies, for example, intersection and difference of relations, special forms of quantification, regular expressions over binary relations. These types of constraints capture a great variety of data models, including the relational, the entity-relationship, and the object-oriented model, all extended with various forms of constraints. They also capture the basic features of the ontology languages used in the context of the Semantic Web.\par We present the following results on both query containment and query answering. We provide a method for query containment under description logic constraints, thus showing that the problem is decidable, and analyze its computational complexity. We prove that query containment is undecidable in the case where we allow inequalities in the right-hand-side query, even for very simple constraints and queries. We show that query answering under description logic constraints can be reduced to query containment, and illustrate how such a reduction provides upper-bound results with respect to both combined and data complexity.", acknowledgement = ack-nhfb, articleno = "22", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "computational compexity; conjunctive queries; description logics; query containment", } @Article{Nanevski:2008:CMT, author = "Aleksandar Nanevski and Frank Pfenning and Brigitte Pientka", title = "Contextual modal type theory", journal = j-TOCL, volume = "9", number = "3", pages = "23:1--23:??", month = jun, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1352582.1352591", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jun 16 14:29:17 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The intuitionistic modal logic of necessity is based on the judgmental notion of categorical truth. In this article we investigate the consequences of relativizing these concepts to explicitly specified contexts. We obtain contextual modal logic and its type-theoretic analogue. Contextual modal type theory provides an elegant, uniform foundation for understanding metavariables and explicit substitutions. We sketch some applications in functional programming and logical frameworks.", acknowledgement = ack-nhfb, articleno = "23", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "intuitionistic modal logic; logical frameworks; type theory", } @Article{Chevalier:2008:CRS, author = "Yannick Chevalier and Ralf K{\"u}sters and Micha{\"e}l Rusinowitch and Mathieu Turuani", title = "Complexity results for security protocols with {Diffie--Hellman} exponentiation and commuting public key encryption", journal = j-TOCL, volume = "9", number = "4", pages = "24:1--24:??", month = aug, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1380572.1380573", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Aug 29 14:02:20 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We show that the insecurity problem for protocols with modular exponentiation and arbitrary products allowed in exponents is NP-complete. This result is based on a protocol and intruder model which is powerful enough to uncover known attacks on the Authenticated Group Diffie--Hellman (A-GDH.2) protocol suite. To prove our results, we develop a general framework in which the Dolev--Yao intruder is extended by generic intruder rules. This framework is also applied to obtain complexity results for protocols with commuting public key encryption.", acknowledgement = ack-nhfb, articleno = "24", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "algebraic properties; complexity; Diffie--Hellman exponentiation; Dolev--Yao model; protocols", } @Article{Wolter:2008:UUA, author = "Frank Wolter and Michael Zakharyaschev", title = "Undecidability of the unification and admissibility problems for modal and description logics", journal = j-TOCL, volume = "9", number = "4", pages = "25:1--25:??", month = aug, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1380572.1380574", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Aug 29 14:02:20 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We show that the unification problem ``is there a substitution instance of a given formula that is provable in a given logic?'' is undecidable for basic modal logics K and K4 extended with the universal modality. It follows that the admissibility problem for inference rules is undecidable for these logics as well. These are the first examples of standard decidable modal logics for which the unification and admissibility problems are undecidable. We also prove undecidability of the unification and admissibility problems for K and K4 with at least two modal operators and nominals (instead of the universal modality), thereby showing that these problems are undecidable for basic hybrid logics. Recently, unification has been introduced as an important reasoning service for description logics. The undecidability proof for K with nominals can be used to show the undecidability of unification for Boolean description logics with nominals (such as ALCO and SHIQO). The undecidability proof for K with the universal modality can be used to show that the unification problem relative to role boxes is undecidable for Boolean description logics with transitive roles, inverse roles, and role hierarchies (such as SHI and SHIQ).", acknowledgement = ack-nhfb, articleno = "25", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "admissible rule; decidability; description logic; hybrid logic; unification", } @Article{Heymans:2008:OAS, author = "Stijn Heymans and Davy {Van Nieuwenborgh} and Dirk Vermeir", title = "Open answer set programming with guarded programs", journal = j-TOCL, volume = "9", number = "4", pages = "26:1--26:??", month = aug, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1380572.1380575", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Aug 29 14:02:20 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Open answer set programming (OASP) is an extension of answer set programming where one may ground a program with an arbitrary superset of the program's constants. We define a fixed-point logic (FPL) extension of Clark's completion such that open answer sets correspond to models of FPL formulas and identify a syntactic subclass of programs, called ({\em loosely\/}) {\em guarded programs}. Whereas reasoning with general programs in OASP is undecidable, the FPL translation of (loosely) guarded programs falls in the decidable (loosely) guarded fixed-point logic ($\mu$(L)GF). Moreover, we reduce normal closed ASP to loosely guarded OASP, enabling, for the first time, a characterization of an answer set semantics by $\mu$LGF formulas.\par We further extend the open answer set semantics for programs with generalized literals. Such {\em generalized programs (gPs)\/} have interesting properties, for example, the ability to express infinity axioms. We restrict the syntax of gPs such that both rules and generalized literals are {\em guarded}. Via a translation to guarded fixed-point logic, we deduce 2-EXPTIME-completeness of satisfiability checking in such {\em guarded gPs\/} (GgPs). {\em Bound GgPs\/} are restricted GgPs with EXPTIME-complete satisfiability checking, but still sufficiently expressive to optimally simulate {\em computation tree logic\/} (CTL). We translate Datalog lite programs to GgPs, establishing equivalence of GgPs under an open answer set semantics, alternation-free $\mu$GF, and Datalog LITE.", acknowledgement = ack-nhfb, articleno = "26", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "answer set programming; fixed-point logic; open domains", } @Article{Shen:2008:RRL, author = "Yi-Dong Shen", title = "Reasoning with recursive loops under the {PLP} framework", journal = j-TOCL, volume = "9", number = "4", pages = "27:1--27:??", month = aug, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1380572.1380576", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Aug 29 14:02:20 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Recursive loops in a logic program present a challenging problem to the PLP (Probabilistic Logic Programming) framework. On the one hand, they loop forever so that the PLP backward-chaining inferences would never stop. On the other hand, they may generate cyclic influences, which are disallowed in Bayesian networks. Therefore, in existing PLP approaches, logic programs with recursive loops are considered to be problematic and thus are excluded. In this article, we propose a novel solution to this problem by making use of recursive loops to build a stationary dynamic Bayesian network. We introduce a new PLP formalism, called a {\em Bayesian knowledge base}. It allows recursive loops and contains logic clauses of the form $A \leftarrow A_1, \ldots, A_l$, {\em true}, {\em Context}, {\em Types}, which naturally formulate the knowledge that the $A_i$'s have direct influences on $A$ in the context {\em Context\/} under the type constraints {\em Types}. We use the well-founded model of a logic program to define the direct influence relation and apply SLG-resolution to compute the space of random variables together with their parental connections. This establishes a clear declarative semantics for a Bayesian knowledge base. We view a logic program with recursive loops as a special temporal model, where backward-chaining cycles of the form $A \leftarrow \ldots A \leftarrow \ldots{}$ are interpreted as feedbacks. This extends existing PLP approaches, which mainly aim at (nontemporal) relational models.", acknowledgement = ack-nhfb, articleno = "27", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Bayesian networks; cyclic influences; logic programming; recursive loops; the well-founded model", } @Article{Seidl:2008:FOV, author = "Helmut Seidl and Kumar Neeraj Verma", title = "Flat and one-variable clauses: {Complexity} of verifying cryptographic protocols with single blind copying", journal = j-TOCL, volume = "9", number = "4", pages = "28:1--28:??", month = aug, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1380572.1380577", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Aug 29 14:02:20 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Cryptographic protocols with single blind copying were defined and modeled by Comon and Cortier using the new class C of first-order clauses. They showed its satisfiability problem to be in 3-DEXPTIME. We improve this result by showing that satisfiability for this class is NEXPTIME-complete, using new resolution techniques. We show satisfiability to be DEXPTIME-complete if clauses are Horn, which is what is required for modeling cryptographic protocols. While translation to Horn clauses only gives a DEXPTIME upper bound for the secrecy problem for these protocols, we further show that this secrecy problem is actually DEXPTIME-complete.", acknowledgement = ack-nhfb, articleno = "28", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "cryptographic protocols; first-order logic; Horn clauses; instantiation-based theorem proving; resolution", } @Article{Alberti:2008:VAI, author = "Marco Alberti and Federico Chesani and Marco Gavanelli and Evelina Lamma and Paola Mello and Paolo Torroni", title = "Verifiable agent interaction in abductive logic programming: {The SCIFF} framework", journal = j-TOCL, volume = "9", number = "4", pages = "29:1--29:??", month = aug, year = "2008", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1380572.1380578", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri Aug 29 14:02:20 MDT 2008", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "SCIFF is a framework thought to specify and verify interaction in open agent societies. The SCIFF language is equipped with a semantics based on abductive logic programming; SCIFF's operational component is a new abductive logic programming proof procedure, also named SCIFF, for reasoning with expectations in dynamic environments. In this article we present the declarative and operational semantics of the SCIFF language, and the termination, soundness, and completeness results of the SCIFF proof procedure, and we demonstrate SCIFF's possible application in the multiagent domain.", acknowledgement = ack-nhfb, articleno = "29", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "abductive logic programming; agent interaction protocols; declarative semantics; formal properties; IFF proof procedure; proof-procedures; SCIFF; SOCS (SOcieties of ComputeeS)", } @Article{Artikis:2009:SNG, author = "Alexander Artikis and Marek Sergot and Jeremy Pitt", title = "Specifying norm-governed computational societies", journal = j-TOCL, volume = "10", number = "1", pages = "1:1--1:??", month = jan, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1459010.1459011", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jan 26 18:05:23 MST 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Electronic markets, dispute resolution and negotiation protocols are three types of application domains that can be viewed as open agent societies. Key characteristics of such societies are agent heterogeneity, conflicting individual goals and unpredictable behavior. Members of such societies may fail to, or even choose not to, conform to the norms governing their interactions. It has been argued that systems of this type should have a formal, declarative, verifiable, and meaningful semantics. We present a theoretical and computational framework being developed for the executable specification of open agent societies. We adopt an external perspective and view societies as instances of normative systems. In this article, we demonstrate how the framework can be applied to specifying and executing a contract-net protocol. The specification is formalized in two action languages, the $C+$ language and the Event Calculus, and executed using respective software implementations, the Causal Calculator and the Society Visualizer. We evaluate our executable specification in the light of the presented case study, discussing the strengths and weaknesses of the employed action languages for the specification of open agent societies.", acknowledgement = ack-nhfb, articleno = "1", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Action language; agent; contract-net; event calculus; executable specification; norm; policy", } @Article{VanDenDries:2009:AC, author = "Lou {Van Den Dries} and Yiannis N. Moschovakis", title = "Arithmetic complexity", journal = j-TOCL, volume = "10", number = "1", pages = "2:1--2:??", month = jan, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1459010.1459012", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jan 26 18:05:23 MST 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We obtain {\em lower bounds\/} on the cost of computing various arithmetic functions and deciding various arithmetic relations from specified primitives. This includes lower bounds for computing the greatest common divisor and deciding coprimeness of two integers, from primitives like addition, subtraction, division with remainder and multiplication. Some of our results are in terms of recursive programs, but they generalize directly to most (plausibly all) algorithms from the specified primitives. Our methods involve some elementary number theory as well as the development of some basic notions and facts about recursive algorithms.", acknowledgement = ack-nhfb, articleno = "2", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "coprimeness; greatest common divisor; Lower bounds for arithmetical problems; recursive programs", } @Article{Yorke-Smith:2009:CCR, author = "Neil Yorke-Smith and Carmen Gervet", title = "Certainty closure: Reliable constraint reasoning with incomplete or erroneous data", journal = j-TOCL, volume = "10", number = "1", pages = "3:1--3:??", month = jan, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1459010.1459013", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jan 26 18:05:23 MST 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Constraint Programming (CP) has proved an effective paradigm to model and solve difficult combinatorial satisfaction and optimization problems from disparate domains. Many such problems arising from the commercial world are permeated by data uncertainty. Existing CP approaches that accommodate uncertainty are less suited to uncertainty arising due to incomplete and erroneous data, because they do not build reliable models and solutions guaranteed to address the user's genuine problem as she perceives it. Other fields such as reliable computation offer combinations of models and associated methods to handle these types of uncertain data, but lack an expressive framework characterizing the resolution methodology independently of the model.\par We present a unifying framework that extends the CP formalism in both model and solutions, to tackle ill-defined combinatorial problems with incomplete or erroneous data. The {\em certainty closure framework\/} brings together modeling and solving methodologies from different fields into the CP paradigm to provide reliable and efficient approaches for uncertain constraint problems. We demonstrate the applicability of the framework on a case study in network diagnosis. We define resolution forms that give generic templates, and their associated operational semantics, to derive practical solution methods for reliable solutions.", acknowledgement = ack-nhfb, articleno = "3", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "closure; Incomplete and erroneous data; reliable solutions; uncertain constraint satisfaction problem", } @Article{Armando:2009:NRR, author = "Alessandro Armando and Maria Paola Bonacina and Silvio Ranise and Stephan Schulz", title = "New results on rewrite-based satisfiability procedures", journal = j-TOCL, volume = "10", number = "1", pages = "4:1--4:??", month = jan, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1459010.1459014", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jan 26 18:05:23 MST 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Program analysis and verification require decision procedures to reason on theories of data structures. Many problems can be reduced to the {\em satisfiability\/} of sets of {\em ground literals\/} in theory $T$. If a sound and complete inference system for first-order logic is guaranteed to {\em terminate\/} on {\em T-satisfiability problems}, any theorem-proving strategy with that system and a fair search plan is a {\em T-satisfiability procedure}. We prove termination of a rewrite-based first-order engine on the theories of {\em records}, {\em integer offsets}, {\em integer offsets modulo\/} and {\em lists}. We give a {\em modularity theorem\/} stating sufficient conditions for termination on a {\em combination of theories}, given termination on each. The above theories, as well as others, satisfy these conditions. We introduce several sets of benchmarks on these theories and their combinations, including both {\em parametric\/} synthetic benchmarks to test {\em scalability}, and real-world problems to test performances on huge sets of literals. We compare the rewrite-based theorem prover $E$ with the validity checkers CVC and CVC Lite. Contrary to the folklore that a general-purpose prover cannot compete with reasoners with built-in theories, the experiments are overall favorable to the theorem prover, showing that not only the rewriting approach is elegant and conceptually simple, but has important practical implications.", acknowledgement = ack-nhfb, articleno = "4", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Automated reasoning; combination of theories; decision procedures; inference; rewriting; satisfiability modulo a theory; scalability; superposition; termination", } @Article{Iocchi:2009:RAA, author = "Luca Iocchi and Thomas Lukasiewicz and Daniele Nardi and Riccardo Rosati", title = "Reasoning about actions with sensing under qualitative and probabilistic uncertainty", journal = j-TOCL, volume = "10", number = "1", pages = "5:1--5:??", month = jan, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1459010.1459015", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jan 26 18:05:23 MST 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We focus on the aspect of sensing in reasoning about actions under qualitative and probabilistic uncertainty. We first define the action language $E$ for reasoning about actions with sensing, which has a semantics based on the autoepistemic description logic {\em ALCK$_{\mbox{NF}}$}, and which is given a formal semantics via a system of deterministic transitions between epistemic states. As an important feature, the main computational tasks in $E$ can be done in linear and quadratic time. We then introduce the action language $E+$ for reasoning about actions with sensing under qualitative and probabilistic uncertainty, which is an extension of $E$ by actions with nondeterministic and probabilistic effects, and which is given a formal semantics in a system of deterministic, nondeterministic, and probabilistic transitions between epistemic states. We also define the notion of a belief graph, which represents the belief state of an agent after a sequence of deterministic, nondeterministic, and probabilistic actions, and which compactly represents a set of unnormalized probability distributions. Using belief graphs, we then introduce the notion of a conditional plan and its goodness for reasoning about actions under qualitative and probabilistic uncertainty. We formulate the problems of optimal and threshold conditional planning under qualitative and probabilistic uncertainty, and show that they are both uncomputable in general. We then give two algorithms for conditional planning in our framework. The first one is always sound, and it is also complete for the special case in which the relevant transitions between epistemic states are cycle-free. The second algorithm is a sound and complete solution to the problem of finite-horizon conditional planning in our framework. Under suitable assumptions, it computes every optimal finite-horizon conditional plan in polynomial time. We also describe an application of our formalism in a robotic-soccer scenario, which underlines its usefulness in realistic applications.", acknowledgement = ack-nhfb, articleno = "5", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "action languages; description logics; imprecise probabilities; qualitative and probabilistic uncertainty; Reasoning about actions; sensing", } @Article{Aceto:2009:FEB, author = "Luca Aceto and Wan Fokkink and Anna Ingolfsdottir and Bas Luttik", title = "A finite equational base for {CCS} with left merge and communication merge", journal = j-TOCL, volume = "10", number = "1", pages = "6:1--6:??", month = jan, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1459010.1459016", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jan 26 18:05:23 MST 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Using the left merge and the communication merge from ACP, we present an equational base (i.e., a ground-complete and $\omega$-complete set of valid equations) for the fragment of CCS without recursion, restriction and relabeling modulo (strong) bisimilarity. Our equational base is finite if the set of actions is finite.", acknowledgement = ack-nhfb, articleno = "6", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Bisimilarity; CCS; communication merge; concurrency; finite equational base; handshaking; left merge; parallel composition; process algebra", } @Article{Kontinen:2009:LCC, author = "Juha Kontinen", title = "A logical characterization of the counting hierarchy", journal = j-TOCL, volume = "10", number = "1", pages = "7:1--7:??", month = jan, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1459010.1459017", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Jan 26 18:05:23 MST 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In this article we give a logical characterization of the counting hierarchy. The counting hierarchy is the analogue of the polynomial hierarchy, the building block being Probabilistic polynomial time PP instead of NP. We show that the extension of first-order logic by second-order majority quantifiers of all arities describes exactly the problems in the counting hierarchy. We also consider extending the characterization to general proportional quantifiers $Q^k_r$ interpreted as ``more than an $r$-fraction of $k$-ary relations''. We show that the result holds for rational numbers of the form $s/2^m$ but for any other $0 < r < 1$, the corresponding logic satisfies the 0-1 law.", acknowledgement = ack-nhfb, articleno = "7", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Counting hierarchy; majority quantifiers; quantifier elimination; the 0-1 law", } @Article{DalLago:2009:GLH, author = "Ugo {Dal Lago}", title = "The geometry of linear higher-order recursion", journal = j-TOCL, volume = "10", number = "2", pages = "8:1--8:??", month = feb, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1462179.1462180", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Feb 25 22:28:54 MST 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Imposing linearity and ramification constraints allows to weaken higher-order (primitive) recursion in such a way that the class of representable functions equals the class of polynomial-time computable functions, as the works by Leivant, Hofmann, and others show. This article shows that fine-tuning these two constraints leads to different expressive strengths, some of them lying well beyond polynomial time. This is done by introducing a new semantics, called algebraic context semantics. The framework stems from Gonthier's original work (itself a model of Girard's geometry of interaction) and turns out to be a versatile and powerful tool for the quantitative analysis of normalization in the lambda calculus with constants and higher-order recursion.", acknowledgement = ack-nhfb, articleno = "8", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Geometry of interaction; higher-order recursion; implicit computational complexity; lambda calculus; type systems", } @Article{Lanotte:2009:PBC, author = "Ruggero Lanotte and Simone Tini", title = "Probabilistic bisimulation as a congruence", journal = j-TOCL, volume = "10", number = "2", pages = "9:1--9:??", month = feb, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1462179.1462181", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Feb 25 22:28:54 MST 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We propose both an SOS transition rule format for the generative model of probabilistic processes, and an SOS transition rule format for the reactive model of the probabilistic processes. Our rule formats guarantee that probabilistic bisimulation is a congruence with respect to process algebra operations. Moreover, our rule format for generative process algebras guarantees that the probability of the moves of a given process, if there are any, sum up to 1, and the rule format for reactive process algebras guarantees that the probability of the moves of a given process labeled with the same action, if there are any, sum up to 1. We show that most operations of the probabilistic process algebras studied in the literature are captured by our formats, which, therefore, have practical applications.", acknowledgement = ack-nhfb, articleno = "9", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Bisimulation; congruence; probabilistic process algebra; transition rule format", } @Article{Gnaedig:2009:TRU, author = "Isabelle Gnaedig and H{\'e}l{\`e}ne Kirchner", title = "Termination of rewriting under strategies", journal = j-TOCL, volume = "10", number = "2", pages = "10:1--10:??", month = feb, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1462179.1462182", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Feb 25 22:28:54 MST 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "A termination proof method for rewriting under strategies, based on an explicit induction on the termination property, is presented and instantiated for the innermost, outermost, and local strategies. Rewriting trees are simulated by proof trees generated with an abstraction mechanism, narrowing and constraints representing sets of ground terms. Abstraction introduces variables to represent normal forms without computing them and to control the narrowing mechanism, well known to easily diverge. The induction ordering is not given a priori, but defined with ordering constraints, incrementally set during the proof. It is established that termination under strategy is equivalent to the construction of finite proof trees schematizing terminating rewriting trees. Sufficient effective conditions to ensure finiteness are studied and the method is illustrated on several examples for each specific strategy.", acknowledgement = ack-nhfb, articleno = "10", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Abstraction; induction; innermost; local strategy; narrowing; ordering constraint; outermost; termination", } @Article{Gabbrielli:2009:CSC, author = "Maurizio Gabbrielli and Maria Chiara Meo", title = "A compositional semantics for {CHR}", journal = j-TOCL, volume = "10", number = "2", pages = "11:1--11:??", month = feb, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1462179.1462183", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Feb 25 22:28:54 MST 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Constraint Handling Rules (CHR) is a committed-choice declarative language which has been designed for writing constraint solvers. A CHR program consists of multiheaded guarded rules which allow to rewrite constraints into simpler ones until a solved form is reached.\par CHR has received considerable attention, both from the practical and from the theoretical side. Nevertheless, due the use of multiheaded clauses, there are several aspects of the CHR semantics which have not been clarified yet. In particular, no compositional semantics for CHR has been defined so far.\par In this article we introduce a fix-point semantics which characterizes the input/output behavior of a CHR program and which is and-compositional, that is, which allows to retrieve the semantics of a conjunctive query from the semantics of its components. Such a semantics can be used as a basis to define incremental and modular analysis and verification tools.", acknowledgement = ack-nhfb, articleno = "11", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Semantics", } @Article{Guerrini:2009:PTC, author = "Stefano Guerrini and Andrea Masini", title = "Proofs, tests and continuation passing style", journal = j-TOCL, volume = "10", number = "2", pages = "12:1--12:??", month = feb, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1462179.1462184", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Feb 25 22:28:54 MST 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The concept of syntactical {\em duality\/} is central in logic. In particular, the duality defined by classical negation, or more syntactically by left and right in sequents, has been widely used to relate logic and computations. We study the proof/test duality proposed by Girard in his 1999 paper on the meaning of logical rules. In detail, starting from the notion of ``test'' proposed by Girard, we develop a notion of test for intuitionistic logic and we give a complete deductive system whose computational interpretation is the target language of the call-by-value and call-by-name continuation passing style translations.", acknowledgement = ack-nhfb, articleno = "12", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "call-by-name; call-by-value; continuations passing style; intutionistic logic; lambda calculus; linear logic; Minimal logic", } @Article{Schroder:2009:PBR, author = "Lutz Schr{\"o}der and Dirk Pattinson", title = "{PSPACE} bounds for rank-1 modal logics", journal = j-TOCL, volume = "10", number = "2", pages = "13:1--13:??", month = feb, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1462179.1462185", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Feb 25 22:28:54 MST 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "For lack of general algorithmic methods that apply to wide classes of logics, establishing a complexity bound for a given modal logic is often a laborious task. The present work is a step towards a general theory of the complexity of modal logics. Our main result is that all rank-1 logics enjoy a shallow model property and thus are, under mild assumptions on the format of their axiomatisation, in {\em PSPACE}. This leads to a unified derivation of tight {\em PSPACE\/} -bounds for a number of logics, including $K$, $KD$, coalition logic, graded modal logic, majority logic, and probabilistic modal logic. Our generic algorithm moreover finds tableau proofs that witness pleasant proof-theoretic properties including a weak subformula property. This generality is made possible by a coalgebraic semantics, which conveniently abstracts from the details of a given model class and thus allows covering a broad range of logics in a uniform way.", acknowledgement = ack-nhfb, articleno = "13", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "coalgebra; resolution; Shallow models", } @Article{Bruscoli:2009:PCD, author = "Paola Bruscoli and Alessio Guglielmi", title = "On the proof complexity of deep inference", journal = j-TOCL, volume = "10", number = "2", pages = "14:1--14:??", month = feb, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1462179.1462186", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Feb 25 22:28:54 MST 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We obtain two results about the proof complexity of deep inference: (1) Deep-inference proof systems are as powerful as Frege ones, even when both are extended with the Tseitin extension rule or with the substitution rule; (2) there are analytic deep-inference proof systems that exhibit an exponential speedup over analytic Gentzen proof systems that they polynomially simulate.", acknowledgement = ack-nhfb, articleno = "14", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Analyticity; calculus of structures; deep inference; Frege systems; Statman tautologies", } @Article{Tripakis:2009:CTB, author = "Stavros Tripakis", title = "Checking timed {B{\"u}chi} automata emptiness on simulation graphs", journal = j-TOCL, volume = "10", number = "3", pages = "15:1--15:??", month = apr, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1507244.1507245", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Apr 13 08:54:35 MDT 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Timed automata [Alur and Dill 1994] comprise a popular model for describing real-time and embedded systems and reasoning formally about them. Efficient model-checking algorithms have been developed and implemented in tools such as Kronos [Daws et al. 1996] or Uppaal [Larsen et al. 1997] for checking safety properties on this model, which amounts to reachability. These algorithms use the so-called zone-closed simulation graph, a finite graph that admits efficient representation and has been recently shown to preserve reachability [Bouyer 2004]. Building upon Bouyer [2004] and our previous work [Bouajjani et al. 1997; Tripakis et al. 2005], we show that this graph can also be used for checking liveness properties, in particular, emptiness of timed B{\"u}chi automata.", acknowledgement = ack-nhfb, articleno = "15", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "chi automata; Formal methods; model checking; property-preserving abstractions; specification languages; timed Bü", } @Article{Demri:2009:LFQ, author = "St{\'e}phane Demri and Ranko Lazi{\'c}", title = "{LTL} with the freeze quantifier and register automata", journal = j-TOCL, volume = "10", number = "3", pages = "16:1--16:??", month = apr, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1507244.1507246", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Apr 13 08:54:35 MDT 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "A data word is a sequence of pairs of a letter from a finite alphabet and an element from an infinite set, where the latter can only be compared for equality. To reason about data words, linear temporal logic is extended by the freeze quantifier, which stores the element at the current word position into a register, for equality comparisons deeper in the formula. By translations from the logic to alternating automata with registers and then to faulty counter automata whose counters may erroneously increase at any time, and from faulty and error-free counter automata to the logic, we obtain a complete complexity table for logical fragments defined by varying the set of temporal operators and the number of registers. In particular, the logic with future-time operators and 1 register is decidable but not primitive recursive over finite data words. Adding past-time operators or 1 more register, or switching to infinite data words, causes undecidability.", acknowledgement = ack-nhfb, articleno = "16", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Computational complexity; expressiveness", } @Article{Bordeaux:2009:GCO, author = "Lucas Bordeaux and Marco Cadoli and Toni Mancini", title = "Generalizing consistency and other constraint properties to quantified constraints", journal = j-TOCL, volume = "10", number = "3", pages = "17:1--17:??", month = apr, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1507244.1507247", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Apr 13 08:54:35 MDT 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Quantified constraints and Quantified Boolean Formulae are typically much more difficult to reason with than classical constraints, because quantifier alternation makes the usual notion of {\em solution\/} inappropriate. As a consequence, basic properties of Constraint Satisfaction Problems (CSPs), such as consistency or substitutability, are not completely understood in the quantified case. These properties are important because they are the basis of most of the reasoning methods used to solve classical (existentially quantified) constraints, and it is desirable to benefit from similar reasoning methods in the resolution of quantified constraints.\par In this article, we show that most of the properties that are used by solvers for CSP can be generalized to quantified CSP. This requires a rethinking of a number of basic concepts; in particular, we propose a notion of {\em outcome\/} that generalizes the classical notion of solution and on which all definitions are based. We propose a systematic study of the relations which hold between these properties, as well as complexity results regarding the decision of these properties. Finally, and since these problems are typically intractable, we generalize the approach used in CSP and propose weaker, easier to check notions based on {\em locality}, which allow to detect these properties incompletely but in polynomial time.", acknowledgement = ack-nhfb, articleno = "17", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Constraint satisfaction; quantified Boolean formulae; quantified constraints", } @Article{Giordano:2009:ATC, author = "Laura Giordano and Valentina Gliozzi and Nicola Olivetti and Gian Luca Pozzato", title = "Analytic tableaux calculi for {KLM} logics of nonmonotonic reasoning", journal = j-TOCL, volume = "10", number = "3", pages = "18:1--18:??", month = apr, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1507244.1507248", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Apr 13 08:54:35 MDT 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We present tableau calculi for the logics of nonmonotonic reasoning defined by Kraus, Lehmann and Magidor (KLM). We give a tableau proof procedure for all KLM logics, namely preferential, loop-cumulative, cumulative, and rational logics. Our calculi are obtained by introducing suitable modalities to interpret conditional assertions. We provide a decision procedure for the logics considered and we study their complexity.", acknowledgement = ack-nhfb, articleno = "18", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Analytic tableaux calculi; nonmonotonic reasoning", } @Article{Ying:2009:AQP, author = "Mingsheng Ying and Yuan Feng and Runyao Duan and Zhengfeng Ji", title = "An algebra of quantum processes", journal = j-TOCL, volume = "10", number = "3", pages = "19:1--19:??", month = apr, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1507244.1507249", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Apr 13 08:54:35 MDT 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We introduce an algebra qCCS of pure quantum processes in which communications by moving quantum states physically are allowed and computations are modeled by super-operators, but no classical data is explicitly involved. An operational semantics of qCCS is presented in terms of (nonprobabilistic) labeled transition systems. Strong bisimulation between processes modeled in qCCS is defined, and its fundamental algebraic properties are established, including uniqueness of the solutions of recursive equations. To model sequential computation in qCCS, a reduction relation between processes is defined. By combining reduction relation and strong bisimulation we introduce the notion of strong reduction-bisimulation, which is a device for observing interaction of computation and communication in quantum systems. Finally, a notion of strong approximate bisimulation (equivalently, strong bisimulation distance) and its reduction counterpart are introduced. It is proved that both approximate bisimilarity and approximate reduction-bisimilarity are preserved by various constructors of quantum processes. This provides us with a formal tool for observing robustness of quantum processes against inaccuracy in the implementation of its elementary gates.", acknowledgement = ack-nhfb, articleno = "19", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "bisimulation; process algebra; quantum communication; Quantum computation; super-operator", } @Article{Bouhoula:2009:SCC, author = "Adel Bouhoula", title = "Simultaneous checking of completeness and ground confluence for algebraic specifications", journal = j-TOCL, volume = "10", number = "3", pages = "20:1--20:??", month = apr, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1507244.1507250", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Apr 13 08:54:35 MDT 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Algebraic specifications provide a powerful method for the specification of abstract data types in programming languages and software systems. Completeness and ground confluence are fundamental notions for building algebraic specifications in a correct and modular way. Related works for checking ground confluence are based on the completion techniques or on the test that all critical pairs between axioms are valid with respect to a sufficient criterion for ground confluence. It is generally accepted that such techniques may be very inefficient, even for very small specifications. Indeed, the completion procedure often diverges and there often exist many critical pairs of the axioms. In this article, we present a procedure for simultaneously checking completeness and ground confluence for specifications with free/nonfree constructors and parameterized specifications. If the specification is not complete or not ground confluent, then our procedure will output the set of patterns on whose ground instances a function is not defined and it can easily identify the rules that break ground confluence. In contrast to previous work, our method does not rely on completion techniques and does not require the computation of critical pairs of the axioms. The method is entirely implemented and allowed us to prove the completeness and the ground confluence of many specifications in a completely automatic way, where related techniques diverge or generate very complex proofs. Our system offers two main components: (i) a completeness and ground confluence analyzer that computes pattern trees of defined functions and may generate some proof obligations; and (ii) a procedure to prove (joinable) inductive conjectures which is used to discharge these proof obligations.", acknowledgement = ack-nhfb, articleno = "20", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "algebraic specifications; Automated deduction; completeness; ground confluence; parameterization; term rewriting systems", } @Article{Giordano:2009:TCP, author = "Laura Giordano and Valentina Gliozzi and Nicola Olivetti and Camilla Schwind", title = "Tableau calculus for preference-based conditional logics: {PCL} and its extensions", journal = j-TOCL, volume = "10", number = "3", pages = "21:1--21:??", month = apr, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1507244.1507251", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Apr 13 08:54:35 MDT 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We present a tableau calculus for some fundamental systems of propositional conditional logics. We consider the conditional logics that can be characterized by {\em preferential\/} semantics (i.e., possible world structures equipped with a family of preference relations). For these logics, we provide a uniform completeness proof of the axiomatization with respect to the semantics, and a uniform labeled tableau procedure.", acknowledgement = ack-nhfb, articleno = "21", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "conditional logics; Tableaux calculi", } @Article{Kawamura:2009:DR, author = "Akitoshi Kawamura", title = "Differential recursion", journal = j-TOCL, volume = "10", number = "3", pages = "22:1--22:??", month = apr, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1507244.1507252", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Mon Apr 13 08:54:35 MDT 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We present a redevelopment of the theory of real-valued recursive functions that was introduced by C. Moore in 1996 by analogy with the standard formulation of the integer-valued recursive functions. While his work opened a new line of research on analog computation, the original paper contained some technical inaccuracies. We discuss possible attempts to remove the ambiguity in the behavior of the operators on partial functions, with a focus on his ``primitive recursive'' functions generated by the {\em differential recursion\/} operator that solves initial value problems. Under a reasonable reformulation, the functions in this class are shown to be analytic and computable in a strong sense in computable analysis. Despite this well-behavedness, the class turns out to be too big to have the originally purported relation to differentially algebraic functions, and hence to C. E. Shannon's model of analog computation.", acknowledgement = ack-nhfb, articleno = "22", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Analog computation; differentially algebraic functions; initial value problems; real recursive functions; transcendentally transcendental functions", } @Article{Baillot:2009:GES, author = "Patrick Baillot and Jean-Yves Marion and Simona Ronchi Della Rocca", title = "Guest editorial: {Special} issue on implicit computational complexity", journal = j-TOCL, volume = "10", number = "4", pages = "23:1--23:??", month = aug, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1555746.1555747", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Aug 11 12:46:55 MDT 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "23", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Arai:2009:NFA, author = "Toshiyasu Arai and Naohi Eguchi", title = "A new function algebra of {EXPTIME} functions by safe nested recursion", journal = j-TOCL, volume = "10", number = "4", pages = "24:1--24:??", month = aug, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1555746.1555748", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Aug 11 12:46:55 MDT 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Bellantoni and Cook have given a function-algebra characterization of the polynomial-time computable functions via an unbounded recursion scheme which is called safe recursion. Inspired by their work, we characterize the exponential-time computable functions with the use of a safe variant of nested recursion.", acknowledgement = ack-nhfb, articleno = "24", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "EXPTIME; implicit computational complexity", } @Article{DalLago:2009:CSL, author = "Ugo {Dal Lago}", title = "Context semantics, linear logic, and computational complexity", journal = j-TOCL, volume = "10", number = "4", pages = "25:1--25:??", month = aug, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1555746.1555749", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Aug 11 12:46:55 MDT 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We show that context semantics can be fruitfully applied to the quantitative analysis of proof normalization in linear logic. In particular, context semantics lets us define the {\em weight\/} of a proof-net as a measure of its inherent complexity: it is both an upper bound to normalization time (modulo a polynomial overhead, independently on the reduction strategy) and a lower bound to the amount of resources needed to compute the normal form. Weights are then exploited in proving strong soundness theorems for various subsystems of linear logic, namely elementary linear logic, soft linear logic, and light linear logic.", acknowledgement = ack-nhfb, articleno = "25", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "geometry of interaction; implicit computational complexity; linear logic", } @Article{Crolard:2009:ELL, author = "Tristan Crolard and Emmanuel Polonowski and Pierre Valarcher", title = "Extending the loop language with higher-order procedural variables", journal = j-TOCL, volume = "10", number = "4", pages = "26:1--26:??", month = aug, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1555746.1555750", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Aug 11 12:46:55 MDT 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We extend Meyer and Ritchie's Loop language with higher-order procedures and procedural variables and we show that the resulting programming language (called Loop$^\omega$) is a natural imperative counterpart of G{\"o}del System T. The argument is two-fold:\par (1) we define a translation of the Loop$^\omega$ language into System T and we prove that this translation actually provides a lock-step simulation,\par (2) using a converse translation, we show that Loop$^\omega$ is expressive enough to encode any term of System T.\par Moreover, we define the ``iteration rank'' of a Loop$^\omega$ program, which corresponds to the classical notion of ``recursion rank'' in System T, and we show that both translations preserve ranks. Two applications of these results in the area of implicit complexity are described.", acknowledgement = ack-nhfb, articleno = "26", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "G{\"o}del System T; higher-order procedures; loop language; procedural variables", } @Article{Marion:2009:SIS, author = "Jean-Yves Marion and Romain P{\'e}choux", title = "Sup-interpretations, a semantic method for static analysis of program resources", journal = j-TOCL, volume = "10", number = "4", pages = "27:1--27:??", month = aug, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1555746.1555751", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Aug 11 12:46:55 MDT 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The sup-interpretation method is proposed as a new tool to control memory resources of first order functional programs with pattern matching by static analysis. It has been introduced in order to increase the intensionality, that is the number of captured algorithms, of a previous method, the quasi-interpretations. Basically, a sup-interpretation provides an upper bound on the size of function outputs. A criterion, which can be applied to terminating as well as nonterminating programs, is developed in order to bound the stack frame size polynomially. Since this work is related to quasi-interpretation, dependency pairs, and size-change principle methods, we compare these notions obtaining several results. The first result is that, given any program, we have heuristics for finding a sup-interpretation when we consider polynomials of bounded degree. Another result consists in the characterizations of the sets of functions computable in polynomial time and in polynomial space. A last result consists in applications of sup-interpretations to the dependency pair and the size-change principle methods.", acknowledgement = ack-nhfb, articleno = "27", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "resources control; static analysis of first-order languages", } @Article{Jones:2009:FCM, author = "Neil D. Jones and Lars Kristiansen", title = "A flow calculus of {\em mwp\/}-bounds for complexity analysis", journal = j-TOCL, volume = "10", number = "4", pages = "28:1--28:??", month = aug, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1555746.1555752", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Aug 11 12:46:55 MDT 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We present a method for certifying that the values computed by an imperative program will be bounded by polynomials in the program's inputs. To this end, we introduce {\em mwp\/}-matrices and define a semantic relation $\models C : M$, where $C$ is a program and $M$ is an {\em mwp\/}-matrix. It follows straightforwardly from our definitions that there exists $M$ such that $\models C : M$ holds iff every value computed by $C$ is bounded by a polynomial in the inputs. Furthermore, we provide a syntactical proof calculus and define the relation $\vdash C : M$ to hold iff there exists a derivation in the calculus where $C : M$ is the bottom line. We prove that $\vdash C : M$ implies $\models C : M$.\par By means of exhaustive proof search, an algorithm can decide if there exists $M$ such that the relation $\vdash C : M$ holds, and thus, our results yield a computational method.", acknowledgement = ack-nhfb, articleno = "28", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "automatable complexity analysis of imperative programs; implicit computational complexity; static program analysis", } @Article{Moyen:2009:RCG, author = "Jean-Yves Moyen", title = "Resource control graphs", journal = j-TOCL, volume = "10", number = "4", pages = "29:1--29:??", month = aug, year = "2009", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1555746.1555753", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Aug 11 12:46:55 MDT 2009", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Resource Control Graphs are an abstract representation of programs. Each state of the program is abstracted by its size, and each instruction is abstracted by the effects it has on the state size whenever it is executed. The abstractions of instruction effects are then used as weights on the arcs of a program's Control Flow Graph.\par Termination is proved by finding decreases in a well-founded order on state-size, in line with other termination analyses, resulting in proofs similar in spirit to those produced by Size Change Termination analysis.\par However, the size of states may also be used to measure the amount of space consumed by the program at each point of execution. This leads to an alternative characterisation of the Non Size Increasing programs, that is, of programs that can compute without allocating new memory.\par This new tool is able to encompass several existing analyses and similarities with other studies, suggesting that even more analyses might be expressible in this framework, thus giving hopes for a generic tool for studying programs.", acknowledgement = ack-nhfb, articleno = "29", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "implicit computational complexity; non-size increasing computation; program analysis; program termination; size change termination", } @Article{Chatterjee:2009:FWR, author = "Krishnendu Chatterjee and Thomas A. Henzinger and Florian Horn", title = "Finitary winning in $\omega$-regular games", journal = j-TOCL, volume = "11", number = "1", pages = "1:1--1:??", month = oct, year = "2009", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Mar 16 08:57:54 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "1", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Schneider-Kamp:2009:ATP, author = "Peter Schneider-Kamp and J{\"u}rgen Giesl and Alexander Serebrenik and Ren{\'e} Thiemann", title = "Automated termination proofs for logic programs by term rewriting", journal = j-TOCL, volume = "11", number = "1", pages = "2:1--2:??", month = oct, year = "2009", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Mar 16 08:57:54 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "2", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Goranko:2009:TBD, author = "Valentin Goranko and Dmitry Shkatov", title = "Tableau-based decision procedures for logics of strategic ability in multiagent systems", journal = j-TOCL, volume = "11", number = "1", pages = "3:1--3:??", month = oct, year = "2009", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Mar 16 08:57:54 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "3", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Benedikt:2009:RTL, author = "Michael Benedikt and Luc Segoufin", title = "Regular tree languages definable in {FO} and in {FO$_{mod}$}", journal = j-TOCL, volume = "11", number = "1", pages = "4:1--4:??", month = oct, year = "2009", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Mar 16 08:57:54 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "4", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Guidi:2009:FS, author = "Ferruccio Guidi", title = "The formal system $\lambda \delta$", journal = j-TOCL, volume = "11", number = "1", pages = "5:1--5:??", month = oct, year = "2009", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Mar 16 08:57:54 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "5", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Pientka:2009:HOT, author = "Brigitte Pientka", title = "Higher-order term indexing using substitution trees", journal = j-TOCL, volume = "11", number = "1", pages = "6:1--6:??", month = oct, year = "2009", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Mar 16 08:57:54 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "6", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Arthan:2009:GFS, author = "Rob Arthan and Ursula Martin and Erik A. Mathiesen and Paulo Oliva", title = "A general framework for sound and complete {Floyd-Hoare} logics", journal = j-TOCL, volume = "11", number = "1", pages = "7:1--7:??", month = oct, year = "2009", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Mar 16 08:57:54 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "7", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bailey:2010:LQV, author = "James Bailey and Guozhu Dong and Anthony Widjaja To", title = "Logical queries over views: {Decidability} and expressiveness", journal = j-TOCL, volume = "11", number = "2", pages = "8:1--8:??", month = jan, year = "2010", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Mar 16 08:57:57 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "8", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Comon-Lundh:2010:DSP, author = "Hubert Comon-Lundh and V{\'e}ronique Cortier and Eugen Z{\~a}linescu", title = "Deciding security properties for cryptographic protocols. Application to key cycles", journal = j-TOCL, volume = "11", number = "2", pages = "9:1--9:??", month = jan, year = "2010", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Mar 16 08:57:57 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "9", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Udrea:2010:AR, author = "Octavian Udrea and Diego Reforgiato Recupero and V. S. Subrahmanian", title = "Annotated {RDF}", journal = j-TOCL, volume = "11", number = "2", pages = "10:1--10:??", month = jan, year = "2010", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Mar 16 08:57:57 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "10", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Adams:2010:WPC, author = "Robin Adams and Zhaohui Luo", title = "Weyl's predicative classical mathematics as a logic-enriched type theory", journal = j-TOCL, volume = "11", number = "2", pages = "11:1--11:??", month = jan, year = "2010", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Mar 16 08:57:57 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "11", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Cosmadakis:2010:UIR, author = "Stavros Cosmadakis and Eugenie Foustoucos and Anastasios Sidiropoulos", title = "Undecidability and intractability results concerning datalog programs and their persistency numbers", journal = j-TOCL, volume = "11", number = "2", pages = "12:1--12:??", month = jan, year = "2010", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Mar 16 08:57:57 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "12", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Tiu:2010:PSS, author = "Alwen Tiu and Dale Miller", title = "Proof search specifications of bisimulation and modal logics for the $\pi$-calculus", journal = j-TOCL, volume = "11", number = "2", pages = "13:1--13:??", month = jan, year = "2010", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Mar 16 08:57:57 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "13", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Eiter:2010:FDN, author = "Thomas Eiter and Mantas {\v{S}}imkus", title = "{FDNC}: {Decidable} nonmonotonic disjunctive logic programs with function symbols", journal = j-TOCL, volume = "11", number = "2", pages = "14:1--14:??", month = jan, year = "2010", CODEN = "????", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Mar 16 08:57:57 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "14", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bodirsky:2010:FAD, author = "Manuel Bodirsky and Jan K{\'a}ra", title = "A fast algorithm and datalog inexpressibility for temporal reasoning", journal = j-TOCL, volume = "11", number = "3", pages = "15:1--15:??", month = may, year = "2010", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1740582.1740583", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri May 14 15:42:49 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We introduce a new tractable temporal constraint language, which strictly contains the Ord-Horn language of B{\"u}rkert and Nebel and the class of AND/OR precedence constraints. The algorithm we present for this language decides whether a given set of constraints is consistent in time that is quadratic in the input size. We also prove that (unlike Ord-Horn) the constraint satisfaction problem of this language cannot be solved by Datalog or by establishing local consistency.", acknowledgement = ack-nhfb, articleno = "15", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "algorithms; computational complexity; Constraint satisfaction; Datalog; Ord-Horn; precedence constraints; temporal reasoning", } @Article{Namjoshi:2010:CCR, author = "Kedar S. Namjoshi and Richard J. Trefler", title = "On the completeness of compositional reasoning methods", journal = j-TOCL, volume = "11", number = "3", pages = "16:1--16:??", month = may, year = "2010", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1740582.1740584", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri May 14 15:42:49 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Hardware systems and reactive software systems can be described as the composition of several concurrently active processes. Automated reasoning based on model checking algorithms can substantially increase confidence in the overall reliability of a system. Direct methods for model checking a concurrent composition, however, usually suffer from the explosion in the number of program states that arises from concurrency. Reasoning compositionally about individual processes helps mitigate this problem. A number of rules have been proposed for compositional reasoning, typically based on an assume-guarantee reasoning paradigm. Reasoning with these rules can be delicate, as some are syntactically circular in nature, in that assumptions and guarantees are mutually dependent. This is known to be a source of unsoundness. In this article, we investigate rules for compositional reasoning from the viewpoint of {\em completeness}. We show that several rules are incomplete: that is, there are properties whose validity cannot be established using (only) these rules. We derive a new, circular, reasoning rule and show it to be sound and complete. We show that the auxiliary assertions needed for completeness need be defined only on the interface of the component processes. We also show that the two main paradigms of circular and noncircular reasoning are closely related, in that a proof of one type can be transformed in a straightforward manner to one of the other type. These results give some insight into the applicability of compositional reasoning methods.", acknowledgement = ack-nhfb, articleno = "16", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "assume-guarantee reasoning; automated reasoning; Compositional reasoning; concurrent systems; syntactically circular reasoning", } @Article{Kahler:2010:DSP, author = "Detlef K{\"a}hler and Ralf K{\"u}sters and Thomas Wilke", title = "Deciding strategy properties of contract-signing protocols", journal = j-TOCL, volume = "11", number = "3", pages = "17:1--17:??", month = may, year = "2010", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1740582.1740585", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri May 14 15:42:49 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Research on the automatic analysis of cryptographic protocols has so far concentrated on reachability properties, such as secrecy and authentication. In this article, we prove that certain game-theoretic security properties, including balance for contract-signing protocols, can be decided in a Dolev--Yao style model with a bounded number of sessions. The decision algorithm that we develop is based on standard constraint-solving procedures, which, in the past, have successfully been employed in tools for reachability properties. Our result thus paves the way for extending these tools to deal with game-theoretic security properties.", acknowledgement = ack-nhfb, articleno = "17", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "automatic security analysis; Contract signing; decidability", } @Article{Dershowitz:2010:CPP, author = "Nachum Dershowitz and Iddo Tzameret", title = "Complexity of propositional proofs under a promise", journal = j-TOCL, volume = "11", number = "3", pages = "18:1--18:??", month = may, year = "2010", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1740582.1740586", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri May 14 15:42:49 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We study --- within the framework of propositional proof complexity --- the problem of certifying unsatisfiability of CNF formulas under the promise that any satisfiable formula has many satisfying assignments, where {\em many\/} stands for an explicitly specified function $\Lambda$ in the number of variables {\em n}. To this end, we develop propositional proof systems under different measures of promises (i.e., different $\Lambda$) as extensions of resolution. This is done by augmenting resolution with axioms that, roughly, can eliminate sets of truth assignments defined by Boolean circuits. We then investigate the complexity of such systems, obtaining an exponential separation in the average case between resolution under different size promises:\par (1) Resolution has polynomial-size refutations for all unsatisfiable 3CNF formulas when the promise is $\epsilon \cdot 2^n$, for any constant 0\par (2) There are no subexponential size resolution refutations for random 3CNF formulas, when the promise is $2^\delta n$, for any constant 0\par ``{\em Goods Satisfactory or Money Refunded\/}''\par --- The Eaton Promise", acknowledgement = ack-nhfb, articleno = "18", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Promise problems; propositional proof complexity; random 3CNF; resolution", } @Article{Ben-Sasson:2010:LBB, author = "Eli Ben-Sasson and Prahladh Harsha", title = "Lower bounds for bounded depth {Frege} proofs via {Pudl{\'a}k--Buss} games", journal = j-TOCL, volume = "11", number = "3", pages = "19:1--19:??", month = may, year = "2010", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1740582.1740587", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri May 14 15:42:49 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We present a simple proof of the bounded-depth Frege proof lower bounds of Pitassi et al. [1993] and Kraj{\'\i}{\v{c}}ek et al. [1995] for the pigeonhole principle. Our method uses the interpretation of proofs as two player games given by Pudl{\'a}k and Buss. Our lower bound is conceptually simpler than previous ones, and relies on tools and intuition that are well known in the context of computational complexity. This makes the lower bound of Pitassi et al. [1993] and Kraj{\'\i}{\v{c}}ek et al. [1995] accessible to the general computational complexity audience. We hope this new view will open new directions for research in proof complexity.", acknowledgement = ack-nhfb, articleno = "19", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Frege proofs; lower bounds; pigeonhole principle; Proof complexity", } @Article{Samer:2010:DLS, author = "Marko Samer and Helmut Veith", title = "On the distributivity of {LTL} specifications", journal = j-TOCL, volume = "11", number = "3", pages = "20:1--20:??", month = may, year = "2010", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1740582.1740588", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Fri May 14 15:42:49 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In this article, we investigate LTL specifications where $\gamma[\varphi \wedge \psi]$ is equivalent to $\gamma[\varphi ] \wedge \gamma[\psi]$ independent of $\varphi$ and $\psi$. Formulas $\gamma$ with this property are called {\em distributive queries\/} because they naturally arise in Chan's seminal approach to temporal logic query solving [Chan 2000]. As recognizing distributive LTL queries is PSpace-complete, we consider distributive fragments of LTL defined by templates as in Buccafurri et al. [2001]. Our main result is a syntactic characterization of distributive LTL queries in terms of LTL templates: we construct a context-free template grammar LTLQ$^x$ which guarantees that all specifications obtained from LTLQ$^x$ are distributive, and all templates not obtained from LTLQ$^x$ have simple nondistributive instantiations.", acknowledgement = ack-nhfb, articleno = "20", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Constraint satisfaction; distributivity; LTL; query solving; strongest solution; syntactic characterization; template characterization; unique solution", } @Article{Kaminski:2010:CSI, author = "Michael Kaminski and Simone Martini", title = "{CSL 2008} special issue", journal = j-TOCL, volume = "11", number = "4", pages = "21:1--21:??", month = jul, year = "2010", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1805950.1805951", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Jul 15 18:17:23 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "21", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Beyersdorff:2010:TKL, author = "Olaf Beyersdorff and Sebastian M{\"u}ller", title = "A tight {Karp--Lipton} collapse result in bounded arithmetic", journal = j-TOCL, volume = "11", number = "4", pages = "22:1--22:??", month = jul, year = "2010", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1805950.1805952", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Jul 15 18:17:23 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Cook and Kraj{\'\i}{\v{c}}ek have recently obtained the following Karp--Lipton collapse result in bounded arithmetic: if the theory {\em PV\/} proves NP $\subseteq$ P/ {\em poly}, then the polynomial hierarchy collapses to the Boolean hierarchy, and this collapse is provable in {\em PV}. Here we show the converse implication, thus answering an open question posed by Cook and Kraj{\'\i}{\v{c}}ek. We obtain this result by formalizing in {\em PV\/} a hard/easy argument of Buhrman et al. [2003].\par In addition, we continue the investigation of propositional proof systems using advice, initiated by Cook and Kraj{\'\i}{\v{c}}ek. In particular, we obtain several optimality results for proof systems using advice. We further show that these optimal systems are equivalent to natural extensions of Frege systems.", acknowledgement = ack-nhfb, articleno = "22", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "advice; bounded arithmetic; extended Frege; Karp--Lipton theorem; optimal propositional proof systems", } @Article{Chatterjee:2010:QL, author = "Krishnendu Chatterjee and Laurent Doyen and Thomas A. Henzinger", title = "Quantitative languages", journal = j-TOCL, volume = "11", number = "4", pages = "23:1--23:??", month = jul, year = "2010", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1805950.1805953", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Jul 15 18:17:23 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Quantitative generalizations of classical languages, which assign to each word a real number instead of a Boolean value, have applications in modeling resource-constrained computation. We use weighted automata (finite automata with transition weights) to define several natural classes of quantitative languages over finite and infinite words; in particular, the real value of an infinite run is computed as the maximum, limsup, liminf, limit average, or discounted sum of the transition weights. We define the classical decision problems of automata theory (emptiness, universality, language inclusion, and language equivalence) in the quantitative setting and study their computational complexity. As the decidability of the language-inclusion problem remains open for some classes of weighted automata, we introduce a notion of quantitative simulation that is decidable and implies language inclusion. We also give a complete characterization of the expressive power of the various classes of weighted automata. In particular, we show that most classes of weighted automata cannot be determinized.", acknowledgement = ack-nhfb, articleno = "23", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "expressiveness; Model checking; quantitative verification; weighted automata", } @Article{Creignou:2010:NBC, author = "Nadia Creignou and Henning Schnoor and Ilka Schnoor", title = "Nonuniform {Boolean} constraint satisfaction problems with cardinality constraint", journal = j-TOCL, volume = "11", number = "4", pages = "24:1--24:??", month = jul, year = "2010", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1805950.1805954", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Jul 15 18:17:23 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We study the computational complexity of Boolean constraint satisfaction problems with cardinality constraint. A Galois connection between clones and coclones has received a lot of attention in the context of complexity considerations for constraint satisfaction problems. This connection does not seem to help when considering constraint satisfaction problems that support in addition a cardinality constraint. We prove that a similar Galois connection, involving a weaker closure operator and partial polymorphisms, can be applied to such problems. Thus, we establish dichotomies for the decision as well as for the counting problems in Schaefer's framework.", acknowledgement = ack-nhfb, articleno = "24", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Computational complexity; constraint satisfaction", } @Article{Dezani-Ciancaglini:2010:IIT, author = "Mariangiola Dezani-Ciancaglini and Roberto {Di Cosmo} and Elio Giovannetti and Makoto Tatsuta", title = "On isomorphisms of intersection types", journal = j-TOCL, volume = "11", number = "4", pages = "25:1--25:??", month = jul, year = "2010", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1805950.1805955", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Jul 15 18:17:23 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The study of type isomorphisms for different $\lambda$-calculi started over twenty years ago, and a very wide body of knowledge has been established, both in terms of results and in terms of techniques. A notable missing piece of the puzzle was the characterization of type isomorphisms in the presence of intersection types. While, at first thought, this may seem to be a simple exercise, it turns out that not only finding the right characterization is not simple, but that the very notion of isomorphism in intersection types is an unexpectedly original element in the previously known landscape, breaking most of the known properties of isomorphisms of the typed $\lambda$-calculus. In particular, isomorphism is not a congruence and types that are equal in the standard models of intersection types may be nonisomorphic.", acknowledgement = ack-nhfb, articleno = "25", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "intersection types; lambda calculus; Type isomorphism", } @Article{Hofmann:2010:PPP, author = "Martin Hofmann and Ulrich Sch{\"o}pp", title = "Pure pointer programs with iteration", journal = j-TOCL, volume = "11", number = "4", pages = "26:1--26:??", month = jul, year = "2010", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1805950.1805956", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Jul 15 18:17:23 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Many logspace algorithms are naturally described as programs that operate on a structured input (e.g., a graph), that store in memory only a constant number of pointers (e.g., to graph nodes) and that do not use pointer arithmetic. Such ``pure pointer algorithms'' thus are a useful abstraction for studying the nature of logspace-computation.\par In this article, we introduce a formal class purple of pure pointer programs and study them on locally ordered graphs. Existing classes of pointer algorithms, such as Jumping Automata on Graphs (jags) or Deterministic Transitive Closure (dtc) logic, often exclude simple programs. purple subsumes these classes and allows for a natural representation of many graph algorithms that access the input graph using a constant number of pure pointers. It does so by providing a primitive for iterating an algorithm over all nodes of the input graph in an unspecified order.\par Since pointers are given as an abstract data type rather than as binary digits we expect that logarithmic-size worktapes cannot be encoded using pointers as is done, for example, in totally ordered dtc-logic. We show that this is indeed the case by proving that the property ``the number of nodes is a power of two,'' which is in logspace, is not representable in purple.", acknowledgement = ack-nhfb, articleno = "26", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "deterministic transitive closure logic; iteration in unspecified order; logarithmic space; pebble automation; Pointer program", } @Article{Horbach:2010:SFD, author = "Matthias Horbach and Christoph Weidenbach", title = "Superposition for fixed domains", journal = j-TOCL, volume = "11", number = "4", pages = "27:1--27:??", month = jul, year = "2010", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1805950.1805957", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Jul 15 18:17:23 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Superposition is an established decision procedure for a variety of first-order logic theories represented by sets of clauses. A satisfiable theory, saturated by superposition, implicitly defines a minimal term-generated model for the theory. Proving universal properties with respect to a saturated theory directly leads to a modification of the minimal model's term-generated domain, as new Skolem functions are introduced. For many applications, this is not desired.\par Therefore, we propose the first superposition calculus that can explicitly represent existentially quantified variables and can thus compute with respect to a given domain. This calculus is sound and refutationally complete in the limit for a first-order fixed domain semantics. For saturated Horn theories and classes of positive formulas, we can even employ the calculus to prove properties of the minimal model itself, going beyond the scope of known superposition-based approaches.", acknowledgement = ack-nhfb, articleno = "27", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "Automated theorem proving; fixed domain semantics; inductionless induction; minimal model semantics; proof by consistency; superposition", } @Article{Saurin:2010:TSC, author = "Alexis Saurin", title = "Typing streams in the {$\Lambda \mu$}-calculus", journal = j-TOCL, volume = "11", number = "4", pages = "28:1--28:??", month = jul, year = "2010", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1805950.1805958", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Jul 15 18:17:23 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "$\Lambda \mu$-calculus is a B{\"o}hm-complete extension of Parigot's $\Lambda \mu$-calculus closely related with delimited control in functional programming. In this article, we investigate the meta-theory of untyped $\Lambda \mu$-calculus by proving confluence of the calculus and characterizing the basic observables for the Separation theorem, {\em canonical normal forms}. Then, we define $\Lambda_s$, a new type system for $\Lambda \mu$-calculus that contains a special type construction for streams, and prove that strong normalization and type preservation hold. Thanks to the new typing discipline of $\Lambda_s$, new computational behaviors can be observed, which were forbidden in previous type systems for $\Lambda \mu$-calculi. Those new typed computational behaviors witness the stream interpretation of $\Lambda \mu$-calculus.", acknowledgement = ack-nhfb, articleno = "28", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", keywords = "$\Lambda$-calculus; $\mu$-calculus; classical $\lambda$ confluence; delimited control; B{\"o}hm theorem; $\lambda \mu$ streams; type system", } @Article{Chockler:2010:EWC, author = "Hana Chockler and Joseph Y. Halpern and Orna Kupferman", title = "Erratum for ``What causes a system to satisfy a specification?''", journal = j-TOCL, volume = "11", number = "4", pages = "29:1--29:??", month = jul, year = "2010", CODEN = "????", DOI = "http://doi.acm.org/10.1145/1805950.1805959", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu Jul 15 18:17:23 MDT 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", note = "See \cite{Chockler:2008:WCS}.", acknowledgement = ack-nhfb, articleno = "29", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Chadha:2010:CGA, author = "Rohit Chadha and Mahesh Viswanathan", title = "A counterexample-guided abstraction-refinement framework for {Markov} decision processes", journal = j-TOCL, volume = "12", number = "1", pages = "1:1--1:??", month = oct, year = "2010", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1838552.1838553", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Nov 23 10:19:25 MST 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The main challenge in using abstractions effectively is to construct a suitable abstraction for the system being verified. One approach that tries to address this problem is that of counterexample guided abstraction refinement (CEGAR), wherein one starts with a coarse abstraction of the system, and progressively refines it, based on invalid counterexamples seen in prior model checking runs, until either an abstraction proves the correctness of the system or a valid counterexample is generated. While CEGAR has been successfully used in verifying nonprobabilistic systems automatically, CEGAR has only recently been investigated in the context of probabilistic systems. The main issues that need to be tackled in order to extend the approach to probabilistic systems is a suitable notion of ``counterexample'', algorithms to generate counterexamples, check their validity, and then automatically refine an abstraction based on an invalid counterexample.", acknowledgement = ack-nhfb, articleno = "1", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Legay:2010:ORM, author = "Axel Legay and Pierre Wolper", title = "On {(Omega-)regular} model checking", journal = j-TOCL, volume = "12", number = "1", pages = "2:1--2:??", month = oct, year = "2010", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1838552.1838554", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Nov 23 10:19:25 MST 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Checking infinite-state systems is frequently done by encoding infinite sets of states as regular languages. Computing such a regular representation of, say, the set of reachable states of a system requires acceleration techniques that can finitely compute the effect of an unbounded number of transitions. Among the acceleration techniques that have been proposed, one finds both specific and generic techniques. Specific techniques exploit the particular type of system being analyzed, for example, a system manipulating queues or integers, whereas generic techniques only assume that the transition relation is represented by a finite-state transducer, which has to be iterated. In this article, we investigate the possibility of using generic techniques in cases where only specific techniques have been exploited so far.", acknowledgement = ack-nhfb, articleno = "2", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Gottlob:2010:MDF, author = "Georg Gottlob and Reinhard Pichler and Fang Wei", title = "Monadic datalog over finite structures of bounded treewidth", journal = j-TOCL, volume = "12", number = "1", pages = "3:1--3:??", month = oct, year = "2010", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1838552.1838555", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Nov 23 10:19:25 MST 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Bounded treewidth and monadic second-order (MSO) logic have proved to be key concepts in establishing fixed-parameter tractability results. Indeed, by Courcelle's Theorem we know that any property of finite structures, which is expressible by an MSO sentence, can be decided in linear time (data complexity) if the structures have bounded treewidth. In principle, Courcelle's Theorem can be applied directly to construct concrete algorithms by transforming the MSO evaluation problem into a tree language recognition problem. The latter can then be solved via a finite tree automaton (FTA). However, this approach has turned out to be problematical, since even relatively simple MSO formulae may lead to a ``state explosion'' of the FTA.", acknowledgement = ack-nhfb, articleno = "3", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Galesi:2010:OSD, author = "Nicola Galesi and Massimo Lauria", title = "Optimality of size-degree tradeoffs for polynomial calculus", journal = j-TOCL, volume = "12", number = "1", pages = "4:1--4:??", month = oct, year = "2010", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1838552.1838556", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Nov 23 10:19:25 MST 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "There are methods to turn short refutations in polynomial calculus (Pc) and polynomial calculus with resolution (Pcr) into refutations of low degree. Bonet and Galesi [1999, 2003] asked if such size-degree tradeoffs for Pc [Clegg et al. 1996; Impagliazzo et al. 1999] and Pcr [Alekhnovich et al. 2004] are optimal. We answer this question by showing a polynomial encoding of the graph ordering principle on m variables which requires Pc and Pcr refutations of degree $\Omega(\sqrt{m})$. Tradeoff optimality follows from our result and from the short refutations of the graph ordering principle in Bonet and Galesi [1999, 2001]. We then introduce the algebraic proof system Pcrk which combines together polynomial calculus and k-DNF resolution (Resk).", acknowledgement = ack-nhfb, articleno = "4", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bistarelli:2010:UMQ, author = "Stefano Bistarelli and Ugo Montanari and Francesca Rossi and Francesco Santini", title = "Unicast and multicast {QoS} routing with soft-constraint logic programming", journal = j-TOCL, volume = "12", number = "1", pages = "5:1--5:??", month = oct, year = "2010", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1838552.1838557", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Nov 23 10:19:25 MST 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We present a formal model to represent and solve the unicast/multicast routing problem in networks with quality-of-service (QoS) requirements. To attain this, first we translate the network adapting it to a weighted graph (unicast) or and-or graph (multicast), where the weight on a connector corresponds to the multidimensional cost of sending a packet on the related network link: each component of the weights vector represents a different QoS metric value (e.g., bandwidth). The second step consists in writing this graph as a program in soft-constraint logic programming (SCLP): the engine of this framework is then able to find the best paths\slash trees by optimizing their costs and solving the constraints imposed on them (e.g., delay $\leq 40$ ms), thus finding a solution to QoS routing problems. C-semiring structures are a convenient tool to model QoS metrics. At last, we provide an implementation of the framework over scale-free networks and we suggest how the performance can be improved. The article highlights the expressivity of SCLP.", acknowledgement = ack-nhfb, articleno = "5", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Billington:2010:ITD, author = "David Billington and Grigoris Antoniou and Guido Governatori and Michael Maher", title = "An inclusion theorem for defeasible logics", journal = j-TOCL, volume = "12", number = "1", pages = "6:1--6:??", month = oct, year = "2010", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1838552.1838558", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Nov 23 10:19:25 MST 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Defeasible reasoning is a computationally simple nonmonotonic reasoning approach that has attracted significant theoretical and practical attention. It comprises a family of logics that capture different intuitions, among them ambiguity propagation versus ambiguity blocking, and the adoption or rejection of team defeat. This article provides a compact presentation of the defeasible logic variants, and derives an inclusion theorem which shows that different notions of provability in defeasible logic form a chain of levels of proof.", acknowledgement = ack-nhfb, articleno = "6", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Cimatti:2010:EGC, author = "Alessandro Cimatti and Alberto Griggio and Roberto Sebastiani", title = "Efficient generation of {Craig} interpolants in satisfiability modulo theories", journal = j-TOCL, volume = "12", number = "1", pages = "7:1--7:??", month = oct, year = "2010", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1838552.1838559", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Nov 23 10:19:25 MST 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The problem of computing Craig interpolants has recently received a lot of interest. In this article, we address the problem of efficient generation of interpolants for some important fragments of first-order logic, which are amenable for effective decision procedures, called satisfiability modulo theory (SMT) solvers. We make the following contributions. First, we provide interpolation procedures for several basic theories of interest: the theories of linear arithmetic over the rationals, difference logic over rationals and integers, and UTVPI over rationals and integers. Second, we define a novel approach to interpolate combinations of theories that applies to the delayed theory combination approach. Efficiency is ensured by the fact that the proposed interpolation algorithms extend state-of-the-art algorithms for satisfiability modulo theories.", acknowledgement = ack-nhfb, articleno = "7", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Furia:2010:TSC, author = "Carlo A. Furia and Matteo Rossi", title = "A theory of sampling for continuous-time metric temporal logic", journal = j-TOCL, volume = "12", number = "1", pages = "8:1--8:??", month = oct, year = "2010", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1838552.1838560", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Nov 23 10:19:25 MST 2010", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "This article revisits the classical notion of sampling in the setting of real-time temporal logics for the modeling and analysis of systems. The relationship between the satisfiability of metric temporal logic (MTL) formulas over continuous-time models and over discrete-time models is studied. It is shown to what extent discrete-time sequences obtained by sampling continuous-time signals capture the semantics of MTL formulas over the two time domains.", acknowledgement = ack-nhfb, articleno = "8", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Gurevich:2011:LIP, author = "Yuri Gurevich and Itay Neeman", title = "Logic of infons: {The} propositional case", journal = j-TOCL, volume = "12", number = "2", pages = "9:1--9:??", month = jan, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1877714.1877715", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jan 26 14:01:49 MST 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Infons are statements viewed as containers of information (rather then representations of truth values). The logic of infons turns out to be a conservative extension of logic known as constructive or intuitionistic. Distributed Knowledge Authorization Language uses additional unary connectives ``p said'' and ``p implied'' where p ranges over principals. Here we investigate infon logic and a narrow but useful primal fragment of it. In both cases, we develop model theory and analyze the derivability problem: Does the given query follow from the given hypotheses? Our more involved technical results are on primal infon logic. We construct an algorithm for the multiple derivability problem: Which of the given queries follow from the given hypotheses? Given a bound on the quotation depth of the hypotheses, the algorithm runs in linear time.", acknowledgement = ack-nhfb, articleno = "9", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Lazic:2011:SAA, author = "Ranko Lazi{\'c}", title = "Safety alternating automata on data words", journal = j-TOCL, volume = "12", number = "2", pages = "10:1--10:??", month = jan, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1877714.1877716", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jan 26 14:01:49 MST 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "A data word is a sequence of pairs of a letter from a finite alphabet and an element from an infinite set, where the latter can only be compared for equality. Safety one-way alternating automata with one register on infinite data words are considered, their nonemptiness is shown to be ExpSpace-complete, and their inclusion decidable but not primitive recursive. The same complexity bounds are obtained for satisfiability and refinement, respectively, for the safety fragment of linear temporal logic with freeze quantification. Dropping the safety restriction, adding past temporal operators, or adding one more register, each causes undecidability.", acknowledgement = ack-nhfb, articleno = "10", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Eiter:2011:WFS, author = "Thomas Eiter and Giovambattista Ianni and Thomas Lukasiewicz and Roman Schindlauer", title = "Well-founded semantics for description logic programs in the {Semantic Web}", journal = j-TOCL, volume = "12", number = "2", pages = "11:1--11:??", month = jan, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1877714.1877717", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jan 26 14:01:49 MST 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The realization of the Semantic Web vision, in which computational logic has a prominent role, has stimulated a lot of research on combining rules and ontologies, which are formulated in different formalisms. In particular, combining logic programming with the Web Ontology Language (OWL), which is a standard based on description logics, emerged as an important issue for linking the Rules and Ontology Layers of the Semantic Web. Nonmonotonic description logic programs (dl-programs) were introduced for such a combination, in which a pair (L,P) of a description logic knowledge base L and a set of rules P with negation as failure is given a model-based semantics that generalizes the answer set semantics of logic programs.", acknowledgement = ack-nhfb, articleno = "11", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Szeider:2011:MSO, author = "Stefan Szeider", title = "Monadic second order logic on graphs with local cardinality constraints", journal = j-TOCL, volume = "12", number = "2", pages = "12:1--12:??", month = jan, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1877714.1877718", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jan 26 14:01:49 MST 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We introduce the class of MSO-LCC problems, which are problems of the following form. Given a graph $G$ and for each vertex $v$ of $G$ a set $\alpha(v)$ of non-negative integers. Is there a set $S$ of vertices or edges of $G$ such that, (1) $S$ satisfies a fixed property expressible in monadic second order logic, and (2) for each vertex $v$ of $G$ the number of vertices\slash edges in $S$ adjacent\slash incident with $v$ belongs to the set $\alpha(v)$? We demonstrate that several hard combinatorial problems such as Lov{\'a}sz's General Factor Problem can be naturally formulated as MSO-LCC problems. Our main result is the polynomial-time tractability of MSO-LCC problems for graphs of bounded treewidth.", acknowledgement = ack-nhfb, articleno = "12", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bauland:2011:TMC, author = "Michael Bauland and Martin Mundhenk and Thomas Schneider and Henning Schnoor and Ilka Schnoor and Heribert Vollmer", title = "The tractability of model checking for {LTL}: The good, the bad, and the ugly fragments", journal = j-TOCL, volume = "12", number = "2", pages = "13:1--13:??", month = jan, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1877714.1877719", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jan 26 14:01:49 MST 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In a seminal paper from 1985, Sistla and Clarke showed that the model-checking problem for Linear Temporal Logic (LTL) is either NP-complete or PSPACE-complete, depending on the set of temporal operators used. If in contrast, the set of propositional operators is restricted, the complexity may decrease. This article systematically studies the model-checking problem for LTL formulae over restricted sets of propositional and temporal operators. For almost all combinations of temporal and propositional operators, we determine whether the model-checking problem is tractable (in PTIME) or intractable (NP-hard). We then focus on the tractable cases, showing that they all are NL-complete or even logspace solvable.", acknowledgement = ack-nhfb, articleno = "13", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Shakarian:2011:APT, author = "Paulo Shakarian and Austin Parker and Gerardo Simari and Venkatramana V. S. Subrahmanian", title = "Annotated probabilistic temporal logic", journal = j-TOCL, volume = "12", number = "2", pages = "14:1--14:??", month = jan, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1877714.1877720", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jan 26 14:01:49 MST 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The semantics of most logics of time and probability is given via a probability distribution over threads, where a thread is a structure specifying what will be true at different points in time (in the future). When assessing the probabilities of statements such as ``Event a will occur within 5 units of time of event b,'' there are many different semantics possible, even when assessing the truth of this statement within a single thread. We introduce the syntax of annotated probabilistic temporal (APT) logic programs and axiomatically introduce the key notion of a frequency function (for the first time) to capture different types of intrathread reasoning, and then provide a semantics for intrathread and interthread reasoning in APT logic programs parameterized by such frequency functions.", acknowledgement = ack-nhfb, articleno = "14", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Urban:2011:MML, author = "Christian Urban and James Cheney and Stefan Berghofer", title = "Mechanizing the metatheory of {LF}", journal = j-TOCL, volume = "12", number = "2", pages = "15:1--15:??", month = jan, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1877714.1877721", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jan 26 14:01:49 MST 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "LF is a dependent type theory in which many other formal systems can be conveniently embedded. However, correct use of LF relies on nontrivial metatheoretic developments such as proofs of correctness of decision procedures for LF's judgments. Although detailed informal proofs of these properties have been published, they have not been formally verified in a theorem prover. We have formalized these properties within Isabelle/HOL using the Nominal Datatype Package, closely following a recent article by Harper and Pfenning. In the process, we identified and resolved a gap in one of the proofs and a small number of minor lacunae in others.", acknowledgement = ack-nhfb, articleno = "15", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Blass:2011:PQB, author = "Andreas Blass and Yuri Gurevich", title = "Persistent queries in the behavioral theory of algorithms", journal = j-TOCL, volume = "12", number = "2", pages = "16:1--16:??", month = jan, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1877714.1877722", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jan 26 14:01:49 MST 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We propose an extension of the behavioral theory of interactive sequential algorithms to deal with the following situation. A query is issued during a certain step, but the step ends before any reply is received. Later, a reply arrives, and later yet the algorithm makes use of this reply. By a persistent query, we mean a query for which a late reply might be used. Our proposal involves issuing, along with a persistent query, a location where a late reply is to be stored. After presenting our proposal in general terms, we discuss the modifications that it requires in the existing axiomatics of interactive sequential algorithms and in the existing syntax and semantics of abstract state machines.", acknowledgement = ack-nhfb, articleno = "16", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Analyti:2011:MPF, author = "Anastasia Analyti and Grigoris Antoniou and Carlos Viegas Damasio", title = "{MWeb}: a principled framework for modular {Web} rule bases and its semantics", journal = j-TOCL, volume = "12", number = "2", pages = "17:1--17:??", month = jan, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1877714.1877723", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Wed Jan 26 14:01:49 MST 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We present a principled framework for modular Web rule bases, called MWeb. According to this framework, each predicate defined in a rule base is characterized by its defining reasoning mode, scope, and exporting rule base list. Each predicate used in a rule base is characterized by its requesting reasoning mode and importing rule base list. For legal MWeb modular rule bases $S$, the MWebAS and MWebWFS semantics of each rule base $s \in S$ with respect to $S$ are defined model-theoretically. These semantics extend the answer set semantics (AS) and the well-founded semantics with explicit negation (WFSX) on ELPs, respectively, keeping all of their semantical and computational characteristics.", acknowledgement = ack-nhfb, articleno = "17", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Nielson:2011:MAC, author = "Flemming Nielson and Sebastian Nanz and Hanne Riis Nielson", title = "Modal abstractions of concurrent behavior", journal = j-TOCL, volume = "12", number = "3", pages = "18:1--18:??", month = may, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1929954.1929955", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu May 12 18:02:30 MDT 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We present an effective algorithm for the automatic construction of finite modal transition systems as abstractions of potentially infinite concurrent processes. Modal transition systems are recognized as valuable abstractions for model checking because they allow for the validation as well as refutation of safety and liveness properties. However, the algorithmic construction of finite abstractions from potentially infinite concurrent processes is a missing link that prevents their more widespread usage for model checking of concurrent systems. Our algorithm is a worklist algorithm using concepts from abstract interpretation and operating upon mappings from sets to intervals in order to express simultaneous over- and underapproximations of the multisets of process actions available in a particular state.", acknowledgement = ack-nhfb, articleno = "18", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Jurdzinski:2011:AAD, author = "Marcin Jurdzi{\'n}ski and Ranko Lazi{\'c}", title = "Alternating automata on data trees and {XPath} satisfiability", journal = j-TOCL, volume = "12", number = "3", pages = "19:1--19:??", month = may, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1929954.1929956", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu May 12 18:02:30 MDT 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "A data tree is an unranked ordered tree whose every node is labeled by a letter from a finite alphabet and an element (``datum'') from an infinite set, where the latter can only be compared for equality. The article considers alternating automata on data trees that can move downward and rightward, and have one register for storing data. The main results are that nonemptiness over finite data trees is decidable but not primitive recursive, and that nonemptiness of safety automata is decidable but not elementary. The proofs use nondeterministic tree automata with faulty counters. Allowing upward moves, leftward moves, or two registers, each causes undecidability.", acknowledgement = ack-nhfb, articleno = "19", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{DeBruijn:2011:ENL, author = "Jos {De Bruijn} and Thomas Eiter and Axel Polleres and Hans Tompits", title = "Embedding nonground logic programs into autoepistemic logic for knowledge-base combination", journal = j-TOCL, volume = "12", number = "3", pages = "20:1--20:??", month = may, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1929954.1929957", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu May 12 18:02:30 MDT 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In the context of the Semantic Web, several approaches for combining ontologies, given in terms of theories of classical first-order logic and rule bases, have been proposed. They either cast rules into classical logic or limit the interaction between rules and ontologies. Autoepistemic logic (AEL) is an attractive formalism which allows overcoming these limitations by serving as a uniform host language to embed ontologies and nonmonotonic logic programs into it. For the latter, so far only the propositional setting has been considered. In this article, we present three embeddings of normal and three embeddings of disjunctive nonground logic programs under the stable model semantics into first-order AEL.", acknowledgement = ack-nhfb, articleno = "20", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bergstra:2011:PA, author = "Jan A. Bergstra and Alban Ponse", title = "Proposition algebra", journal = j-TOCL, volume = "12", number = "3", pages = "21:1--21:??", month = may, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1929954.1929958", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu May 12 18:02:30 MDT 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Sequential propositional logic deviates from conventional propositional logic by taking into account that during the sequential evaluation of a propositional statement, atomic propositions may yield different Boolean values at repeated occurrences. We introduce ``free valuations'' to capture this dynamics of a propositional statement's environment. The resulting logic is phrased as an equationally specified algebra rather than in the form of proof rules, and is named ``proposition algebra.'' It is strictly more general than Boolean algebra to the extent that the classical connectives fail to be expressively complete in the sequential case. The four axioms for free valuation congruence are then combined with other axioms in order define a few more valuation congruences that gradually identify more propositional statements, up to static valuation congruence (which is the setting of conventional propositional logic).", acknowledgement = ack-nhfb, articleno = "21", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Santo:2011:CMS, author = "Jos{\'e} Esp{\'\i}rito Santo and Lu{\'\i}s Pinto", title = "A calculus of multiary sequent terms", journal = j-TOCL, volume = "12", number = "3", pages = "22:1--22:??", month = may, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1929954.1929959", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Thu May 12 18:02:30 MDT 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Multiary sequent terms were originally introduced as a tool for proving termination of permutative conversions in cut-free sequent calculus. This work develops the language of multiary sequent terms into a term calculus for the computational (Curry-Howard) interpretation of a fragment of sequent calculus with cuts and cut-elimination rules. The system, called generalized multiary $\lambda$-calculus, is a rich extension of the $\lambda$-calculus where the computational content of the sequent calculus format is explained through an enlarged form of the application constructor. Such constructor exhibits the features of multiarity (the ability to form lists of arguments) and generality (the ability to prescribe a kind of continuation).", acknowledgement = ack-nhfb, articleno = "22", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Burger:2011:SIS, author = "Lutz Stra{\ss} Burger and Alessio Guglielmi", title = "A system of interaction and structure {IV}: The exponentials and decomposition", journal = j-TOCL, volume = "12", number = "4", pages = "23:1--23:??", month = jul, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1970398.1970399", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Jul 19 16:34:58 MDT 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We study a system, called NEL, which is the mixed commutative/noncommutative linear logic BV augmented with linear logic's exponentials. Equivalently, NEL is MELL augmented with the noncommutative self-dual connective seq. In this article, we show a basic compositionality property of NEL, which we call decomposition. This result leads to a cut-elimination theorem, which is proved in the next article of this series. To control the induction measure for the theorem, we rely on a novel technique that extracts from NEL proofs the structure of exponentials, into what we call !?-Flow-Graphs.", acknowledgement = ack-nhfb, articleno = "23", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bulatov:2011:CCC, author = "Andrei A. Bulatov", title = "Complexity of conservative constraint satisfaction problems", journal = j-TOCL, volume = "12", number = "4", pages = "24:1--24:??", month = jul, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1970398.1970400", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Jul 19 16:34:58 MDT 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In a constraint satisfaction problem (CSP), the aim is to find an assignment of values to a given set of variables, subject to specified constraints. The CSP is known to be NP-complete in general. However, certain restrictions on the form of the allowed constraints can lead to problems solvable in polynomial time. Such restrictions are usually imposed by specifying a constraint language, that is, a set of relations that are allowed to be used as constraints. A principal research direction aims to distinguish those constraint languages that give rise to tractable CSPs from those that do not. We achieve this goal for the important version of the CSP, in which the set of values for each individual variable can be restricted arbitrarily.", acknowledgement = ack-nhfb, articleno = "24", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Ferraris:2011:LPP, author = "Paolo Ferraris", title = "Logic programs with propositional connectives and aggregates", journal = j-TOCL, volume = "12", number = "4", pages = "25:1--25:??", month = jul, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1970398.1970401", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Jul 19 16:34:58 MDT 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Answer set programming (ASP) is a logic programming paradigm that can be used to solve complex combinatorial search problems. Aggregates are an ASP construct that plays an important role in many applications. Defining a satisfactory semantics of aggregates turned out to be a difficult problem, and in this article we propose a new approach, based on an analogy between aggregates and propositional connectives. First we extend the definition of an answer set/stable model to cover arbitrary propositional theories; then we define aggregates on top of them both as primitive constructs and as abbreviations for formulas.", acknowledgement = ack-nhfb, articleno = "25", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Gascon:2011:UMC, author = "Adri{\`a} Gasc{\'o}n and Guillem Godoy and Manfred Schmidt-Schauss", title = "Unification and matching on compressed terms", journal = j-TOCL, volume = "12", number = "4", pages = "26:1--26:??", month = jul, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1970398.1970402", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Jul 19 16:34:58 MDT 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Term unification plays an important role in many areas of computer science, especially in those related to logic. The universal mechanism of grammar-based compression for terms, in particular the so-called singleton tree grammars (STGAs), have recently drawn considerable attention. Using STGs, terms of exponential size and height can be represented in linear space. Furthermore, the term representation by directed acyclic graphs (dags) can be efficiently simulated. The present article is the result of an investigation on term unification and matching when the terms given as input are represented using different compression mechanisms for terms such as dags and singleton tree grammars.", acknowledgement = ack-nhfb, articleno = "26", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bojanczyk:2011:TVL, author = "Miko{\l}aj Boja{\'n}czyk and Claire David and Anca Muscholl and Thomas Schwentick and Luc Segoufin", title = "Two-variable logic on data words", journal = j-TOCL, volume = "12", number = "4", pages = "27:1--27:??", month = jul, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1970398.1970403", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Jul 19 16:34:58 MDT 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In a data word each position carries a label from a finite alphabet and a data value from some infinite domain. This model has been already considered in the realm of semistructured data, timed automata, and extended temporal logics. This article shows that satisfiability for the two-variable fragment FO2($\sim$, $<$, $+1$) of first-order logic with data equality test $\sim$ is decidable over finite and infinite data words. Here $+1$ and $<$ are the usual successor and order predicates, respectively. The satisfiability problem is shown to be at least as hard as reachability in Petri nets.", acknowledgement = ack-nhfb, articleno = "27", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Chatterjee:2011:QCP, author = "Krishnendu Chatterjee and Luca {De Alfaro} and Thomas A. Henzinger", title = "Qualitative concurrent parity games", journal = j-TOCL, volume = "12", number = "4", pages = "28:1--28:??", month = jul, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1970398.1970404", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Jul 19 16:34:58 MDT 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We consider two-player games played on a finite state space for an infinite number of rounds. The games are concurrent: in each round, the two players (player 1 and player 2) choose their moves independently and simultaneously; the current state and the two moves determine the successor state. We consider $\omega$-regular winning conditions specified as parity objectives. Both players are allowed to use randomization when choosing their moves. We study the computation of the limit-winning set of states, consisting of the states where the sup-inf value of the game for player 1 is 1: in other words, a state is limit-winning if player 1 can ensure a probability of winning arbitrarily close to 1.", acknowledgement = ack-nhfb, articleno = "28", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Khan:2011:LIS, author = "Md. Aquil Khan and Mohua Banerjee", title = "Logics for information systems and their dynamic extensions", journal = j-TOCL, volume = "12", number = "4", pages = "29:1--29:??", month = jul, year = "2011", CODEN = "????", DOI = "http://dx.doi.org/10.1145/1970398.1970405", ISSN = "1529-3785 (print), 1557-945X (electronic)", bibdate = "Tue Jul 19 16:34:58 MDT 2011", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The article proposes logics for information systems, which provide information about a set of objects regarding a set of attributes. Both ``complete'' and ``incomplete'' information systems are dealt with. The language of these logics contains modal operators, and constants corresponding to attributes and attribute values. Sound and complete deductive systems for these logics are presented, and the problem of decidability is addressed. Furthermore, notions of information and information update are defined, and dynamic extensions of the above logics are presented to accommodate these notions. A set of reduction axioms enables us to obtain a complete axiomatization of the dynamic logics.", acknowledgement = ack-nhfb, articleno = "29", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Gurfinkel:2012:RVB, author = "Arie Gurfinkel and Marsha Chechik", title = "Robust Vacuity for Branching Temporal Logic", journal = j-TOCL, volume = "13", number = "1", pages = "1:1--1:??", month = jan, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2071368.2071369", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Jan 26 16:08:06 MST 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "There is a growing interest in techniques for detecting whether a logic specification is satisfied too easily, or vacuously. For example, the specification ``every request is eventually followed by an acknowledgment'' is satisfied vacuously by a system that never generates any requests. Vacuous satisfaction misleads users of model-checking into thinking that a system is correct. It is a serious problem in practice. There are several existing definitions of vacuity. Originally, Beer et al. [1997] formalized vacuity as insensitivity to syntactic perturbation (syntactic vacuity). This formulation captures the intuition of ``vacuity'' when applied to a single occurrence of a subformula. Armoni et al.", acknowledgement = ack-nhfb, articleno = "1", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Baelde:2012:LGF, author = "David Baelde", title = "Least and Greatest Fixed Points in Linear Logic", journal = j-TOCL, volume = "13", number = "1", pages = "2:1--2:??", month = jan, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2071368.2071370", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Jan 26 16:08:06 MST 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The first-order theory of MALL (multiplicative, additive linear logic) over only equalities is a well-structured but weak logic since it cannot capture unbounded (infinite) behavior. Instead of accounting for unbounded behavior via the addition of the exponentials (! and ?) , we add least and greatest fixed point operators. The resulting logic, which we call $\mu$MALL, satisfies two fundamental proof theoretic properties: we establish weak normalization for it, and we design a focused proof system that we prove complete with respect to the initial system. That second result provides a strong normal form for cut-free proof structures that can be used, for example, to help automate proof search.", acknowledgement = ack-nhfb, articleno = "2", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{vandenBerg:2012:TSM, author = "Benno van den Berg and Richard Garner", title = "Topological and Simplicial Models of Identity Types", journal = j-TOCL, volume = "13", number = "1", pages = "3:1--3:??", month = jan, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2071368.2071371", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Jan 26 16:08:06 MST 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In this paper we construct new categorical models for the identity types of Martin-L{\``o}f type theory, in the categories Top of topological spaces and SSet of simplicial sets. We do so building on earlier work of Awodey and Warren [2009], which has suggested that a suitable environment for the interpretation of identity types should be a category equipped with a weak factorization system in the sense of Bousfield--Quillen. It turns out that this is not quite enough for a sound model, due to some subtle coherence issues concerned with stability under substitution; and so our first task is to introduce a slightly richer structure, which we call a homotopy-theoretic model of identity types, and to prove that this is sufficient for a sound interpretation.", acknowledgement = ack-nhfb, articleno = "3", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Gelade:2012:SCI, author = "Wouter Gelade and Frank Neven", title = "Succinctness of the Complement and Intersection of Regular Expressions", journal = j-TOCL, volume = "13", number = "1", pages = "4:1--4:??", month = jan, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2071368.2071372", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Jan 26 16:08:06 MST 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We study the succinctness of the complement and intersection of regular expressions. In particular, we show that when constructing a regular expression defining the complement of a given regular expression, a double exponential size increase cannot be avoided. Similarly, when constructing a regular expression defining the intersection of a fixed and an arbitrary number of regular expressions, an exponential and double exponential size increase, respectively, cannot be avoided. All mentioned lower bounds improve the existing ones by one exponential and are tight in the sense that the target expression can be constructed in the corresponding time class, that is, exponential or double exponential time.", acknowledgement = ack-nhfb, articleno = "4", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Madelaine:2012:CPF, author = "Florent Madelaine and Barnaby Martin", title = "The Complexity of Positive First-Order Logic without Equality", journal = j-TOCL, volume = "13", number = "1", pages = "5:1--5:??", month = jan, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2071368.2071373", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Jan 26 16:08:06 MST 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We study the complexity of evaluating positive equality-free sentences of first-order (FO) logic over a fixed, finite structure B. This may be seen as a natural generalisation of the nonuniform quantified constraint satisfaction problem QCSP(B). We introduce surjective hyper-endomorphisms and use them in proving a Galois connection that characterizes definability in positive equality-free FO. Through an algebraic method, we derive a complete complexity classification for our problems as B ranges over structures of size at most three. Specifically, each problem either is in L, is NP-complete, is co-NP-complete, or is Pspace-complete.", acknowledgement = ack-nhfb, articleno = "5", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{DiGiusto:2012:EPM, author = "Cinzia {Di Giusto} and Maurizio Gabbrielli and Maria Chiara Meo", title = "On the Expressive Power of Multiple Heads in {CHR}", journal = j-TOCL, volume = "13", number = "1", pages = "6:1--6:??", month = jan, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2071368.2071374", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Jan 26 16:08:06 MST 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Constraint Handling Rules (CHR) is a committed-choice declarative language that has been originally designed for writing constraint solvers and is nowadays a general purpose language. CHR programs consist of multiheaded guarded rules which allow to rewrite constraints into simpler ones until a solved form is reached. Many empirical evidences suggest that multiple heads augment the expressive power of the language, however no formal result in this direction has been proved, so far. In the first part of this article we analyze the Turing completeness of CHR with respect to the underlying constraint theory. We prove that if the constraint theory is powerful enough then restricting to single head rules does not affect the Turing completeness of the language.", acknowledgement = ack-nhfb, articleno = "6", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Ghafari:2012:RPP, author = "Naghmeh Ghafari and Arie Gurfinkel and Nils Klarlund and Richard Trefler", title = "Reachability Problems in Piecewise {FIFO} Systems", journal = j-TOCL, volume = "13", number = "1", pages = "7:1--7:??", month = jan, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2071368.2071375", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Jan 26 16:08:06 MST 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Systems consisting of several finite components that communicate via unbounded perfect FIFO channels (i.e., FIFO systems) arise naturally in modeling distributed systems. Despite well-known difficulties in analyzing such systems, they are of significant interest as they can describe a wide range of communication protocols. In this article, we study the problem of computing the set of reachable states of a FIFO system composed of piecewise components. This problem is closely related to calculating the set of all possible channel contents, that is, the limit language, for each control location. We present an algorithm for calculating the limit language of a system with a single communication channel.", acknowledgement = ack-nhfb, articleno = "7", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Keiren:2012:SAB, author = "Jeroen J. A. Keiren and Michel A. Reniers and Tim A. C. Willemse", title = "Structural Analysis of {Boolean} Equation Systems", journal = j-TOCL, volume = "13", number = "1", pages = "8:1--8:??", month = jan, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2071368.2071376", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Jan 26 16:08:06 MST 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We analyze the problem of solving Boolean equation systems through the use of structure graphs. The latter are obtained through an elegant set of Plotkin-style deduction rules. Our main contribution is that we show that equation systems with bisimilar structure graphs have the same solution. We show that our work conservatively extends earlier work, conducted by Keiren and Willemse, in which dependency graphs were used to analyze a subclass of Boolean equation systems, viz., equation systems in standard recursive form.", acknowledgement = ack-nhfb, articleno = "8", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Nguyen:2012:CPD, author = "Phuong Nguyen and Stephen Cook", title = "The Complexity of Proving the {Discrete Jordan Curve Theorem}", journal = j-TOCL, volume = "13", number = "1", pages = "9:1--9:??", month = jan, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2071368.2071377", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Jan 26 16:08:06 MST 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The Jordan curve theorem (JCT) states that a simple closed curve divides the plane into exactly two connected regions. We formalize and prove the theorem in the context of grid graphs, under different input settings, in theories of bounded arithmetic that correspond to small complexity classes. The theory V0(2) (corresponding to AC0(2)) proves that any set of edges that form disjoint cycles divides the grid into at least two regions. The theory V0 (corresponding to AC0) proves that any sequence of edges that form a simple closed curve divides the grid into exactly two regions.", acknowledgement = ack-nhfb, articleno = "9", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Levy:2012:NUH, author = "Jordi Levy and Mateu Villaret", title = "Nominal Unification from a Higher-Order Perspective", journal = j-TOCL, volume = "13", number = "2", pages = "10:1--10:??", month = apr, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2159531.2159532", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Apr 19 17:50:31 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Nominal logic is an extension of first-order logic with equality, name-binding, renaming via name-swapping and freshness of names. Contrarily to lambda-terms, in nominal terms, bindable names, called atoms, and instantiable variables are considered as distinct entities. Moreover, atoms are capturable by instantiations, breaking a fundamental principle of the lambda-calculus. Despite these differences, nominal unification can be seen from a higher-order perspective. From this view, we show that nominal unification can be quadratically reduced to a particular fragment of higher-order unification problems: higher-order pattern unification. We also prove that the translation preserves most generality of unifiers.", acknowledgement = ack-nhfb, articleno = "10", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Berardi:2012:IRN, author = "Stefano Berardi and Ugo de'Liguoro", title = "Interactive Realizers: a New Approach to Program Extraction from Nonconstructive Proofs", journal = j-TOCL, volume = "13", number = "2", pages = "11:1--11:??", month = apr, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2159531.2159533", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Apr 19 17:50:31 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We propose a realizability interpretation of a system for quantier free arithmetic which is equivalent to the fragment of classical arithmetic without nested quantifiers, called here EM$_1$ -arithmetic. We interpret classical proofs as interactive learning strategies, namely as processes going through several stages of knowledge and learning by interacting with the ``nature,'' represented by the standard interpretation of closed atomic formulas, and with each other. We obtain in this way a program extraction method by proof interpretation, which is faithful with respect to proofs, in the sense that it is compositional and that it does not need any translation.", acknowledgement = ack-nhfb, articleno = "11", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Etessami:2012:MCR, author = "Kousha Etessami and Mihalis Yannakakis", title = "Model Checking of Recursive Probabilistic Systems", journal = j-TOCL, volume = "13", number = "2", pages = "12:1--12:??", month = apr, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2159531.2159534", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Apr 19 17:50:31 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Recursive Markov Chains (RMCs) are a natural abstract model of procedural probabilistic programs and related systems involving recursion and probability. They succinctly define a class of denumerable Markov chains that generalize several other stochastic models, and they are equivalent in a precise sense to probabilistic Pushdown Systems. In this article, we study the problem of model checking an RMC against an $\omega$-regular specification, given in terms of a B{\"u}chi automaton or a Linear Temporal Logic (LTL) formula. Namely, given an RMC A and a property, we wish to know the probability that an execution of A satisfies the property. We establish a number of strong upper bounds, as well as lower bounds, both for qualitative problems (is the probability = 1, or = 0?), and for quantitative problems (is the probability {$>$}= p?, or, approximate the probability to within a desired precision). The complexity upper bounds we obtain for automata and LTL properties are similar, although the algorithms are different. We present algorithms for the qualitative model checking problem that run in polynomial space in the size | A | of the RMC and exponential time in the size of the property (the automaton or the LTL formula). For several classes of RMCs, including single-exit RMCs (a class that encompasses some well-studied stochastic models, for instance, stochastic context-free grammars) the algorithm runs in polynomial time in | A |. For the quantitative model checking problem, we present algorithms that run in polynomial space in the RMC and exponential space in the property. For the class of linearly recursive RMCs we can compute the exact probability in time polynomial in the RMC and exponential in the property. For deterministic automata specifications, all our complexities in the specification come down by one exponential. For lower bounds, we show that the qualitative model checking problem, even for a fixed RMC, is already EXPTIME-complete. On the other hand, even for simple reachability analysis, we know from our prior work that our PSPACE upper bounds in A can not be improved substantially without a breakthrough on a well-known open problem in the complexity of numerical computation.", acknowledgement = ack-nhfb, articleno = "12", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Shakarian:2012:APT, author = "Paulo Shakarian and Gerardo I. Simari and V. S. Subrahmanian", title = "Annotated Probabilistic Temporal Logic: Approximate Fixpoint Implementation", journal = j-TOCL, volume = "13", number = "2", pages = "13:1--13:??", month = apr, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2159531.2159535", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Apr 19 17:50:31 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Annotated Probabilistic Temporal (APT) logic programs support building applications where we wish to reason about statements of the form ``Formula $G$ becomes true with a probability in the range $[ L, U ]$ within (or in exactly) $\Delta t$ time units after formula $F$ became true.'' In this paper, we present a sound, but incomplete fixpoint operator that can be used to check consistency and entailment in APT logic programs. We present the first implementation of APT-logic programs and evaluate both its compute time and convergence on a suite of 23 ground APT-logic programs that were automatically learned from two real-world data sets. In both cases, the APT-logic programs contained up to 1,000 ground rules. In one data set, entailment problems were solved on average in under 0.1 seconds per ground rule, while in the other, it took up to 1.3 seconds per ground rule. Consistency was also checked in a reasonable amount of time. When discussing entailment of APT-logic formulas, convergence of the fixpoint operator refers to $( U - L )$ being below a certain threshold. We show that on virtually all of the 23 automatically generated APT-logic programs, convergence was quick---often in just 2--3 iterations of the fixpoint operator. Thus, our implementation is a practical first step towards checking consistency and entailment in temporal probabilistic logics without independence or Markovian assumptions.", acknowledgement = ack-nhfb, articleno = "13", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Ferrari:2012:SRI, author = "Mauro Ferrari and Camillo Fiorentini and Guido Fiorino", title = "Simplification Rules for Intuitionistic Propositional Tableaux", journal = j-TOCL, volume = "13", number = "2", pages = "14:1--14:??", month = apr, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2159531.2159536", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Apr 19 17:50:31 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The implementation of a logic requires, besides the definition of a calculus and a decision procedure, the development of techniques to reduce the search space. In this article we introduce some simplification rules for Intuitionistic propositional logic that try to replace a formula with an equi-satisfiable ``simpler'' one with the aim to reduce the search space. Our results are proved via semantical techniques based on Kripke models. We also provide an empirical evaluation of their impact on implementations.", acknowledgement = ack-nhfb, articleno = "14", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Danicic:2012:CDD, author = "Sebastian Danicic and Robert M. Hierons and Michael R. Laurence", title = "Complexity of Data Dependence Problems for Program Schemas with Concurrency", journal = j-TOCL, volume = "13", number = "2", pages = "15:1--15:??", month = apr, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2159531.2159537", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Apr 19 17:50:31 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The problem of deciding whether one point in a program is data dependent upon another is fundamental to program analysis and has been widely studied. In this article we consider this problem at the abstraction level of program schemas in which computations occur in the Herbrand domain of terms and predicate symbols, which represent arbitrary predicate functions, are allowed. Given a vertex l in the flowchart of a schema S having only equality (variable copying) assignments, and variables v, w, we show that it is PSPACE-hard to decide whether there exists an execution of a program defined by S in which v holds the initial value of w at least one occurrence of l on the path of execution, with membership in PSPACE holding provided there is a constant upper bound on the arity of any predicate in S. We also consider the `dual' problem in which v is required to hold the initial value of w at every occurrence of l, for which the analogous results hold. Additionally, the former problem for programs with nondeterministic branching (in effect, free schemas) in which assignments with functions are allowed is proved to be polynomial-time decidable provided a constant upper bound is placed upon the number of occurrences of the concurrency operator in the schemas being considered. This result is promising since many concurrent systems have a relatively small number of threads (concurrent processes), especially when compared with the number of statements they have.", acknowledgement = ack-nhfb, articleno = "15", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Nordstrom:2012:RSP, author = "Jakob Nordstr{\"o}m", title = "On the Relative Strength of Pebbling and Resolution", journal = j-TOCL, volume = "13", number = "2", pages = "16:1--16:??", month = apr, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2159531.2159538", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Apr 19 17:50:31 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The last decade has seen a revival of interest in pebble games in the context of proof complexity. Pebbling has proven to be a useful tool for studying resolution-based proof systems when comparing the strength of different subsystems, showing bounds on proof space, and establishing size-space trade-offs. The typical approach has been to encode the pebble game played on a graph as a CNF formula and then argue that proofs of this formula must inherit (various aspects of) the pebbling properties of the underlying graph. Unfortunately, the reductions used here are not tight. To simulate resolution proofs by pebblings, the full strength of nondeterministic black-white pebbling is needed, whereas resolution is only known to be able to simulate deterministic black pebbling. To obtain strong results, one therefore needs to find specific graph families which either have essentially the same properties for black and black-white pebbling (not at all true in general) or which admit simulations of black-white pebblings in resolution. This article contributes to both these approaches. First, we design a restricted form of black-white pebbling that can be simulated in resolution and show that there are graph families for which such restricted pebblings can be asymptotically better than black pebblings. This proves that, perhaps somewhat unexpectedly, resolution can strictly beat black-only pebbling, and in particular that the space lower bounds on pebbling formulas in Ben-Sasson and Nordstr{\"o}m [2008] are tight. Second, we present a versatile parametrized graph family with essentially the same properties for black and black-white pebbling, which gives sharp simultaneous trade-offs for black and black-white pebbling for various parameter settings. Both of our contributions have been instrumental in obtaining the time-space trade-off results for resolution-based proof systems in Ben-Sasson and Nordstr{\"o}m [2011].", acknowledgement = ack-nhfb, articleno = "16", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Creignou:2012:CRF, author = "Nadia Creignou and Arne Meier and Heribert Vollmer and Michael Thomas", title = "The Complexity of Reasoning for Fragments of Autoepistemic Logic", journal = j-TOCL, volume = "13", number = "2", pages = "17:1--17:??", month = apr, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2159531.2159539", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Apr 19 17:50:31 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Autoepistemic logic extends propositional logic by the modal operator $L$. A formula $\varphi$ that is preceded by an $L$ is said to be ``believed.'' The logic was introduced by Moore in 1985 for modeling an ideally rational agent's behavior and reasoning about his own beliefs. In this article we analyze all Boolean fragments of autoepistemic logic with respect to the computational complexity of the three most common decision problems expansion existence, brave reasoning and cautious reasoning. As a second contribution we classify the computational complexity of checking that a given set of formulae characterizes a stable expansion and that of counting the number of stable expansions of a given knowledge base. We improve the best known $\Delta_2^p$-upper bound on the former problem to completeness for the second level of the Boolean hierarchy. To the best of our knowledge, this is the first paper analyzing counting problem for autoepistemic logic.", acknowledgement = ack-nhfb, articleno = "17", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Gaboardi:2012:ICP, author = "Marco Gaboardi and Jean-Yves Marion and Simona Ronchi Della Rocca", title = "An Implicit Characterization of {PSPACE}", journal = j-TOCL, volume = "13", number = "2", pages = "18:1--18:??", month = apr, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2159531.2159540", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Thu Apr 19 17:50:31 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We present a type system for an extension of lambda calculus with a conditional construction, named STA$_B$, that characterizes the PSPACE class. This system is obtained by extending STA, a type assignment for lambda-calculus inspired by Lafont's Soft Linear Logic and characterizing the PTIME class. We extend STA by means of a ground type and terms for Booleans and conditional. The key issue in the design of the type system is to manage the contexts in the rule for conditional in an additive way. Thanks to this rule, we are able to program polynomial time Alternating Turing Machines. From the well-known result APTIME = PSPACE, it follows that STA$_B$ is complete for PSPACE. Conversely, inspired by the simulation of Alternating Turing machines by means of Deterministic Turing machine, we introduce a call-by-name evaluation machine with two memory devices in order to evaluate programs in polynomial space. As far as we know, this is the first characterization of PSPACE that is based on lambda calculus and light logics.", acknowledgement = ack-nhfb, articleno = "18", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Gelade:2012:DCF, author = "Wouter Gelade and Marcel Marquardt and Thomas Schwentick", title = "The dynamic complexity of formal languages", journal = j-TOCL, volume = "13", number = "3", pages = "19:1--19:??", month = aug, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2287718.2287719", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 24 16:18:32 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The article investigates the power of the dynamic complexity classes D ynFO, DynQF, and DynPROP over string languages. The latter two classes contain problems that can be maintained using quantifier-free first-order updates, with and without auxiliary functions, respectively. It is shown that the languages maintainable in DynPROP are exactly the regular languages, even when allowing arbitrary precomputation. This enables lower bounds for DynPROP and separates DynPROP from DynQF and DynFO. Further, it is shown that any context-free language can be maintained in DynFO and a number of specific context-free languages, for example all Dyck-languages, are maintainable in DynQF. Furthermore, the dynamic complexity of regular tree languages is investigated and some results concerning arbitrary structures are obtained: There exist first-order definable properties which are not maintainable in DynPROP. On the other hand, any existential first-order property can be maintained in DynQF when allowing precomputation.", acknowledgement = ack-nhfb, articleno = "19", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Dowek:2012:PNL, author = "Gilles Dowek and Murdoch J. Gabbay", title = "Permissive-nominal logic: First-order logic over nominal terms and sets", journal = j-TOCL, volume = "13", number = "3", pages = "20:1--20:??", month = aug, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2287718.2287720", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 24 16:18:32 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Permissive-Nominal Logic (PNL) is an extension of first-order predicate logic in which term-formers can bind names in their arguments. This allows for direct axiomatizations with binders, such as of the $\lambda$-binder of the lambda-calculus or the $\forall$-binder of first-order logic. It also allows us to finitely axiomatize arithmetic, and similarly to axiomatize ``nominal'' datatypes-with-binding. Just like first- and higher-order logic, equality reasoning is not necessary to $\alpha$-rename. This gives PNL much of the expressive power of higher-order logic, but models and derivations of PNL are first-order in character, and the logic seems to strike a good balance between expressivity and simplicity.", acknowledgement = ack-nhfb, articleno = "20", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Baader:2012:LDL, author = "Franz Baader and Silvio Ghilardi and Carsten Lutz", title = "{LTL} over description logic axioms", journal = j-TOCL, volume = "13", number = "3", pages = "21:1--21:??", month = aug, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2287718.2287721", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 24 16:18:32 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Most of the research on temporalized Description Logics (DLs) has concentrated on the case where temporal operators can be applied to concepts, and sometimes additionally to TBox axioms and ABox assertions. The aim of this article is to study temporalized DLs where temporal operators on TBox axioms and ABox assertions are available, but temporal operators on concepts are not. While the main application of existing temporalized DLs is the representation of conceptual models that explicitly incorporate temporal aspects, the family of DLs studied in this article addresses applications that focus on the temporal evolution of data and of ontologies. Our results show that disallowing temporal operators on concepts can significantly decrease the complexity of reasoning. In particular, reasoning with rigid roles (whose interpretation does not change over time) is typically undecidable without such a syntactic restriction, whereas our logics are decidable in elementary time even in the presence of rigid roles. We analyze the effects on computational complexity of dropping rigid roles, dropping rigid concepts, replacing temporal TBoxes with global ones, and restricting the set of available temporal operators. In this way, we obtain a novel family of temporalized DLs whose complexity ranges from 2- ExpTime-complete via NExpTime-complete to ExpTime-complete.", acknowledgement = ack-nhfb, articleno = "21", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{More:2012:CCG, author = "Sara Miner More and Pavel Naumov", title = "Calculus of cooperation and game-based reasoning about protocol privacy", journal = j-TOCL, volume = "13", number = "3", pages = "22:1--22:??", month = aug, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2287718.2287722", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 24 16:18:32 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The article introduces a new formal system, the calculus of cooperation, for reasoning about coalitions of players in a certain class of games. The calculus is an extension of the propositional intuitionistic logic that adds a coalition parameter to intuitionistic implication. The system is shown to be sound and complete with respect to a game semantics. One intended application of the calculus of cooperation is the verification of privacy properties in multiparty computation protocols. The article argues that such properties can be established by providing a set of strategies for a non-zero-sum, perfect information game based on the protocol. It concludes with several examples of such verifications formalized in the calculus of cooperation.", acknowledgement = ack-nhfb, articleno = "22", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Makino:2012:DII, author = "Kazuhisa Makino and Hirotaka Ono", title = "Deductive inference for the interiors and exteriors of {Horn} theories", journal = j-TOCL, volume = "13", number = "3", pages = "23:1--23:??", month = aug, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2287718.2287723", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 24 16:18:32 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In this article, we investigate deductive inference for interiors and exteriors of Horn knowledge bases, where interiors and exteriors were introduced by Makino and Ibaraki [1996] to study stability properties of knowledge bases. We present a linear time algorithm for deduction for interiors and show that deduction is coNP-complete for exteriors. Under model-based representation, we show that the deduction problem for interiors is NP-complete while the one for exteriors is coNP-complete. As for Horn envelopes of exteriors, we show that it is linearly solvable under model-based representation, while it is coNP-complete under formula-based representation. We also discuss polynomially solvable cases for all the intractable problems.", acknowledgement = ack-nhfb, articleno = "23", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Kjos-Hanssen:2012:ACE, author = "Bj{\o}rn Kjos-Hanssen and Frank Stephan and Jason Teutsch", title = "Arithmetic complexity via effective names for random sequences", journal = j-TOCL, volume = "13", number = "3", pages = "24:1--24:??", month = aug, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2287718.2287724", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 24 16:18:32 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We investigate enumerability properties for classes of sets which permit recursive, lexicographically increasing approximations, or left-r.e. sets. In addition to pinpointing the complexity of left-r.e. Martin-L{\"o}f, computably, Schnorr, and Kurtz random sets, weakly 1-generics and their complementary classes, we find that there exist characterizations of the third and fourth levels of the arithmetic hierarchy purely in terms of these notions. More generally, there exists an equivalence between arithmetic complexity and existence of numberings for classes of left-r.e. sets with shift-persistent elements. While some classes (such as Martin-L{\"o}f randoms and Kurtz nonrandoms) have left-r.e. numberings, there is no canonical, or acceptable, left-r.e. numbering for any class of left-r.e. randoms. Finally, we note some fundamental differences between left-r.e. numberings for sets and reals.", acknowledgement = ack-nhfb, articleno = "24", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bianco:2012:GCT, author = "Alessandro Bianco and Fabio Mogavero and Aniello Murano", title = "Graded computation tree logic", journal = j-TOCL, volume = "13", number = "3", pages = "25:1--25:??", month = aug, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2287718.2287725", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 24 16:18:32 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In modal logics, graded (world) modalities have been deeply investigated as a useful framework for generalizing standard existential and universal modalities in such a way that they can express statements about a given number of immediately accessible worlds. These modalities have been recently investigated with respect to the $\mu$ Calculus, which have provided succinctness, without affecting the satisfiability of the extended logic, that is, it remains solvable in ExpTime. A natural question that arises is how logics that allow reasoning about paths could be affected by considering graded path modalities. In this article, we investigate this question in the case of the branching-time temporal logic CTL (GCTL, for short). We prove that, although GCTL is more expressive than CTL, the satisfiability problem for GCTL remains solvable in ExpTime, even in the case that the graded numbers are coded in binary. This result is obtained by exploiting an automata-theoretic approach, which involves a model of alternating automata with satellites. The satisfiability result turns out to be even more interesting as we show that GCTL is at least exponentially more succinct than graded $\mu$ Calculus.", acknowledgement = ack-nhfb, articleno = "25", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Goldblatt:2012:WSP, author = "Robert Goldblatt and Marcel Jackson", title = "Well-structured program equivalence is highly undecidable", journal = j-TOCL, volume = "13", number = "3", pages = "26:1--26:??", month = aug, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2287718.2287726", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 24 16:18:32 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We show that strict deterministic propositional dynamic logic with intersection is highly undecidable, solving a problem in the Stanford Encyclopedia of Philosophy. In fact we show something quite a bit stronger. We introduce the construction of program equivalence, which returns the value $\top$ precisely when two given programs are equivalent on halting computations. We show that virtually any variant of propositional dynamic logic has a $\Pi_1^1$-hard validity problem if it can express even just the equivalence of well-structured programs with the empty program skip. We also show, in these cases, that the set of propositional statements valid over finite models is not recursively enumerable, so there is not even an axiomatization for finitely valid propositions.", acknowledgement = ack-nhfb, articleno = "26", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Alur:2012:AAA, author = "Rajeev Alur and Pavol Cern{\'y} and Scott Weinstein", title = "Algorithmic analysis of array-accessing programs", journal = j-TOCL, volume = "13", number = "3", pages = "27:1--27:??", month = aug, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2287718.2287727", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 24 16:18:32 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "For programs whose data variables range over Boolean or finite domains, program verification is decidable, and this forms the basis of recent tools for software model checking. In this article, we consider algorithmic verification of programs that use Boolean variables, and in addition, access a single read-only array whose length is potentially unbounded, and whose elements range over an unbounded data domain. We show that the reachability problem, while undecidable in general, is (1) Pspace-complete for programs in which the array-accessing for-loops are not nested, (2) decidable for a restricted class of programs with doubly nested loops. The second result establishes connections to automata and logics defining languages over data words.", acknowledgement = ack-nhfb, articleno = "27", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Chatzikokolakis:2012:ESG, author = "Konstantinos Chatzikokolakis and Sophia Knight and Catuscia Palamidessi and Prakash Panangaden", title = "Epistemic Strategies and Games on Concurrent Processes", journal = j-TOCL, volume = "13", number = "4", pages = "28:1--28:??", month = oct, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2362355.2362356", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Oct 23 06:11:18 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We develop a game semantics for process algebra with two interacting agents. The purpose of our semantics is to make manifest the role of knowledge and information flow in the interactions between agents and to control the information available to interacting agents. We define games and strategies on process algebras, so that two agents interacting according to their strategies determine the execution of the process, replacing the traditional scheduler. We show that different restrictions on strategies represent different amounts of information being available to a scheduler. We also show that a certain class of strategies corresponds to the syntactic schedulers of Chatzikokolakis and Palamidessi, which were developed to overcome problems with traditional schedulers modelling interaction. The restrictions on these strategies have an explicit epistemic flavour.", acknowledgement = ack-nhfb, articleno = "28", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Boker:2012:TCB, author = "Udi Boker and Orna Kupferman", title = "Translating to {Co--B{\"u}chi} Made Tight, Unified, and Useful", journal = j-TOCL, volume = "13", number = "4", pages = "29:1--29:??", month = oct, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2362355.2362357", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Oct 23 06:11:18 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We solve the longstanding open problems of the blow-up involved in the translations, when possible, of a nondeterministic B{\"u}chi word automaton (NBW) to a nondeterministic co-B{\"u}chi word automaton (NCW) and to a deterministic co-B{\"u}chi word automaton (DCW). For the NBW to NCW translation, the currently known upper bound is $2^{O(n \log n)}$ and the lower bound is $1.5 n$. We improve the upper bound to $n 2^n$ and describe a matching lower bound of $2^{\Omega(n)}$. For the NBW to DCW translation, the currently known upper bound is $2^{O(n \log n)}$. We improve it to $2^{O(n)}$, which is asymptotically tight. Both of our upper-bound constructions are based on a simple subset construction, do not involve intermediate automata with richer acceptance conditions, and can be implemented symbolically. We continue and solve the open problems of translating nondeterministic Streett, Rabin, Muller, and parity word automata to NCW and to DCW. Going via an intermediate NBW is not optimal and we describe direct, simple, and asymptotically tight constructions, involving a $2^{\Theta(n)}$ blow-up. The constructions are variants of the subset construction, providing a unified approach for translating all common classes of automata to NCW and DCW. Beyond the theoretical importance of the results, we point to numerous applications of the new constructions. In particular, they imply a simple subset-construction based translation, when possible, of LTL to deterministic B{\"u}chi word automata.", acknowledgement = ack-nhfb, articleno = "29", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Peppas:2012:MMB, author = "Pavlos Peppas and Costas D. Koutras and Mary-Anne Williams", title = "Maps in Multiple Belief Change", journal = j-TOCL, volume = "13", number = "4", pages = "30:1--30:??", month = oct, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2362355.2362358", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Oct 23 06:11:18 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Multiple Belief Change extends the classical AGM framework for Belief Revision introduced by Alchourron, Gardenfors, and Makinson in the early '80s. The extended framework includes epistemic input represented as a (possibly infinite) set of sentences, as opposed to a single sentence assumed in the original framework. The transition from single to multiple epistemic input worked out well for the operation of belief revision. The AGM postulates and the system-of-spheres model were adequately generalized and so was the representation result connecting the two. In the case of belief contraction however, the transition was not as smooth. The generalized postulates for contraction, which were shown to correspond precisely to the generalized partial meet model, failed to match up to the generalized epistemic entrenchment model. The mismatch was fixed with the addition of an extra postulate, called the limit postulate, that relates contraction by multiple epistemic input to a series of contractions by single epistemic input. The new postulate however creates problems on other fronts. First, the limit postulate needs to be mapped into appropriate constraints in the partial meet model. Second, via the Levi and Harper Identities, the new postulate translates into an extra postulate for multiple revision, which in turn needs to be characterized in terms of systems of spheres. Both these open problems are addressed in this article. In addition, the limit postulate is compared with a similar condition in the literature, called (K*F), and is shown to be strictly weaker than it. An interesting aspect of our results is that they reveal a profound connection between rationality in multiple belief change and the notion of an elementary set of possible worlds (closely related to the notion of an elementary class of models from classical logic).", acknowledgement = ack-nhfb, articleno = "30", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Durand:2012:HDL, author = "Arnaud Durand and Juha Kontinen", title = "Hierarchies in Dependence Logic", journal = j-TOCL, volume = "13", number = "4", pages = "31:1--31:??", month = oct, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2362355.2362359", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Oct 23 06:11:18 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We study fragments $D( k \forall)$ and $D(k-{\rm dep})$ of dependence logic defined either by restricting the number $k$ of universal quantifiers or the width of dependence atoms in formulas. We find the sublogics of existential second-order logic corresponding to these fragments of dependence logic. We also show that, for any fixed signature, the fragments $D(k \forall)$ give rise to an infinite hierarchy with respect to expressive power. On the other hand, for the fragments $D(k-{\rm dep})$, a hierarchy theorem is obtained only in the case the signature is also allowed to vary. For any fixed signature, this question is open and is related to the so-called Spectrum Arity Hierarchy Conjecture.", acknowledgement = ack-nhfb, articleno = "31", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Madalinska-Bugaj:2012:GQE, author = "Ewa Madali{\'n}ska-Bugaj and Linh Anh Nguyen", title = "A Generalized {QSQR} Evaluation Method for {Horn} Knowledge Bases", journal = j-TOCL, volume = "13", number = "4", pages = "32:1--32:??", month = oct, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2362355.2362360", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Oct 23 06:11:18 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We generalize the QSQR evaluation method to give the first set-oriented depth-first evaluation method for Horn knowledge bases. The resulting procedure closely simulates SLD-resolution (to take advantages of the goal-directed approach) and highly exploits set-at-a-time tabling. Our generalized QSQR evaluation procedure is sound and complete. It does not use adornments and annotations. To deal with function symbols, our procedure uses iterative deepening search, which iteratively increases term-depth bound for atoms and substitutions occurring in the computation. When the term-depth bound is fixed, our evaluation procedure runs in polynomial time in the size of extensional relations.", acknowledgement = ack-nhfb, articleno = "32", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Schockaert:2012:FEL, author = "Steven Schockaert and Jeroen Janssen and Dirk Vermeir", title = "Fuzzy Equilibrium Logic: Declarative Problem Solving in Continuous Domains", journal = j-TOCL, volume = "13", number = "4", pages = "33:1--33:??", month = oct, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2362355.2362361", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Oct 23 06:11:18 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In this article, we introduce fuzzy equilibrium logic as a generalization of both Pearce equilibrium logic and fuzzy answer set programming. The resulting framework combines the capability of equilibrium logic to declaratively specify search problems, with the capability of fuzzy logics to model continuous domains. We show that our fuzzy equilibrium logic is a proper generalization of both Pearce equilibrium logic and fuzzy answer set programming, and we locate the computational complexity of the main reasoning tasks at the second level of the polynomial hierarchy. We then provide a reduction from the problem of finding fuzzy equilibrium logic models to the problem of solving a particular bilevel mixed integer program (biMIP), allowing us to implement reasoners by reusing existing work from the operations research community. To illustrate the usefulness of our framework from a theoretical perspective, we show that a well-known characterization of strong equivalence in Pearce equilibrium logic generalizes to our setting, yielding a practical method to verify whether two fuzzy answer set programs are strongly equivalent. Finally, to illustrate its application potential, we show how fuzzy equilibrium logic can be used to find strong Nash equilibria, even when players have a continuum of strategies at their disposal. As a second application example, we show how to find abductive explanations from Lukasiewicz logic theories.", acknowledgement = ack-nhfb, articleno = "33", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Figueira:2012:DDX, author = "Diego Figueira", title = "Decidability of Downward {XPath}", journal = j-TOCL, volume = "13", number = "4", pages = "34:1--34:??", month = oct, year = "2012", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2362355.2362362", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Oct 23 06:11:18 MDT 2012", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We investigate the satisfiability problem for downward-XPath, the fragment of XPath that includes the child and descendant axes, and tests for (in)equality of attributes' values. We prove that this problem is decidable, EXPTIME-complete. These bounds also hold when path expressions allow closure under the Kleene star operator. To obtain these results, we introduce a Downward Data automata model (DD automata) over trees with data, which has a decidable emptiness problem. Satisfiability of downward-XPath can be reduced to the emptiness problem of DD automata and hence its decidability follows. Although downward-XPath does not include any horizontal axis, DD automata are more expressive and can perform some horizontal tests. Thus, we show that the satisfiability remains in EXPTIME even in the presence of the regular constraints expressible by DD automata. However, the same problem in the presence of any regular constraint is known to have a nonprimitive recursive complexity. Finally, we give the exact complexity of the satisfiability problem for several fragments of downward-XPath.", acknowledgement = ack-nhfb, articleno = "34", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Betz:2013:LLB, author = "Hariolf Betz and Thom Fr{\"u}hwirth", title = "Linear-Logic Based Analysis of Constraint Handling Rules with Disjunction", journal = j-TOCL, volume = "14", number = "1", pages = "1:1--1:??", month = feb, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2422085.2422086", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Feb 20 16:38:47 MST 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Constraint Handling Rules (CHR) is a declarative rule-based programming language that has cut out its niche over the course of the last 20 years. It generalizes concurrent constraint logic programming to multiple heads, thus closing the gap to multiset transformation systems. Its popular extension CHR with Disjunction (CHR$ \vee $ ) is a multiparadigm declarative programming language that allows embedding of Horn programs with SLD resolution. We analyze the assets and the limitations of the classical declarative semantics of CHR$ \vee $ and highlight its natural relationship with linear-logic. We furthermore develop two linear-logic semantics for CHR$ \vee $ that differ in the reasoning domain for which they are instrumental. We show their idempotence and their soundness and completeness with respect to the operational semantics. We show how to apply the linear-logic semantics to decide program properties and to reason about operational equivalence of CHR$ \vee $ programs.", acknowledgement = ack-nhfb, articleno = "1", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Krotzsch:2013:CHD, author = "Markus Kr{\"o}tzsch and Sebastian Rudolph and Pascal Hitzler", title = "Complexities of {Horn} Description Logics", journal = j-TOCL, volume = "14", number = "1", pages = "2:1--2:??", month = feb, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2422085.2422087", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Feb 20 16:38:47 MST 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Description logics (DLs) have become a prominent paradigm for representing knowledge in a variety of application areas, partly due to their ability to achieve a favourable balance between expressivity of the logic and performance of reasoning. Horn description logics are obtained, roughly speaking, by disallowing all forms of disjunctions. They have attracted attention since their (worst-case) data complexities are in general lower than those of their non-Horn counterparts, which makes them attractive for reasoning with large sets of instance data (ABoxes). It is therefore natural to ask whether Horn DLs also provide advantages for schema (TBox) reasoning, that is, whether they also feature lower combined complexities. This article settles this question for a variety of Horn DLs. An example of a tractable Horn logic is the DL underlying the ontology language OWL RL, which we characterize as the Horn fragment of the description logic SROIQ without existential quantifiers. If existential quantifiers are allowed, however, many Horn DLs become intractable. We find that Horn- ALC already has the same worst-case complexity as ALC, that is, ExpTime, but we also identify various DLs for which reasoning is PSpace-complete. As a side effect, we derive simplified syntactic definitions of Horn DLs for which we exploit suitable normal form transformations.", acknowledgement = ack-nhfb, articleno = "2", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Chen:2013:CLM, author = "Xiaoping Chen and Jianmin Ji and Fangzhen Lin", title = "Computing Loops with at Most One External Support Rule", journal = j-TOCL, volume = "14", number = "1", pages = "3:1--3:??", month = feb, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2422085.2422088", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Feb 20 16:38:47 MST 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "A consequence of a logic program under answer set semantics is one that is true for all answer sets. This article considers using loop formulas to compute some of these consequences in order to increase the efficiency of answer set solvers. Since computing loop formulas are in general intractable, we consider only loops with either no external support or at most one external support, as their loop formulas are either unit or binary clauses. We show that for disjunctive logic programs, loop formulas of loops with no external support can be computed in polynomial time, and that an iterative procedure using unit propagation on these formulas and the program completion computes the well-founded models in the case of normal logic programs and the least fixed point of a simplification operator used by DLV for disjunctive logic programs. For loops with at most one external support, their loop formulas can be computed in polynomial time for normal logic programs, but are NP-hard for disjunctive programs. So for normal logic programs, we have a procedure similar to the iterative one for loops without any external support, but for disjunctive logic programs, we present a polynomial approximation algorithm. All these algorithms have been implemented, and our experiments show that for certain logic programs, the consequences computed by our algorithms can significantly speed up current ASP solvers cmodels, clasp, and DLV.", acknowledgement = ack-nhfb, articleno = "3", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Baudet:2013:YGT, author = "Mathieu Baudet and V{\'e}ronique Cortier and St{\'e}phanie Delaune", title = "{YAPA}: a Generic Tool for Computing Intruder Knowledge", journal = j-TOCL, volume = "14", number = "1", pages = "4:1--4:??", month = feb, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2422085.2422089", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Feb 20 16:38:47 MST 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Reasoning about the knowledge of an attacker is a necessary step in many formal analyses of security protocols. In the framework of the applied pi-calculus, as in similar languages based on equational logics, knowledge is typically expressed by two relations: deducibility and static equivalence. Several decision procedures have been proposed for these relations under a variety of equational theories. However, each theory has its particular algorithm, and none has been implemented so far. We provide a generic procedure for deducibility and static equivalence that takes as input any convergent rewrite system. We show that our algorithm covers most of the existing decision procedures for convergent theories. We also provide an efficient implementation and compare it briefly with the tools ProVerif and KiSs.", acknowledgement = ack-nhfb, articleno = "4", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{McKinley:2013:PNH, author = "Richard McKinley", title = "Proof Nets for {Herbrand}'s Theorem", journal = j-TOCL, volume = "14", number = "1", pages = "5:1--5:??", month = feb, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2422085.2422090", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Feb 20 16:38:47 MST 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "This article explores Herbrand's theorem as the source of a natural notion of abstract proof object for classical logic, embodying the ``essence'' of a sequent calculus proof. We see how to view a calculus of abstract Herbrand proofs (Herbrand nets) as an analytic proof system with syntactic cut-elimination. Herbrand nets can also be seen as a natural generalization of Miller's expansion tree proofs to a setting including cut. We demonstrate sequentialization of Herbrand nets into a sequent calculus {LK{$_H$}}; each net corresponds to an equivalence class of {LK{$_H$}} proofs under natural proof transformations. A surprising property of our cut-reduction algorithm is that it is non-confluent despite not supporting the usual examples of non-confluent reduction in classical logic.", acknowledgement = ack-nhfb, articleno = "5", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Larchey-Wendling:2013:NPS, author = "Dominique Larchey-Wendling and Didier Galmiche", title = "Nondeterministic Phase Semantics and the Undecidability of {Boolean} {BI}", journal = j-TOCL, volume = "14", number = "1", pages = "6:1--6:??", month = feb, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2422085.2422091", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Feb 20 16:38:47 MST 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We solve the open problem of the decidability of Boolean BI logic (BBI), which can be considered the core of separation and spatial logics. For this, we define a complete phase semantics suitable for BBI and characterize it as trivial phase semantics. We deduce an embedding between trivial phase semantics for intuitionistic linear logic (ILL) and Kripke semantics for BBI. We single out the elementary fragment of ILL, which is both undecidable and complete for trivial phase semantics. Thus, we obtain the undecidability of BBI.", acknowledgement = ack-nhfb, articleno = "6", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bonsangue:2013:SCA, author = "Marcello M. Bonsangue and Stefan Milius and Alexandra Silva", title = "Sound and Complete Axiomatizations of Coalgebraic Language Equivalence", journal = j-TOCL, volume = "14", number = "1", pages = "7:1--7:??", month = feb, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2422085.2422092", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Feb 20 16:38:47 MST 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Coalgebras provide a uniform framework for studying dynamical systems, including several types of automata. In this article, we make use of the coalgebraic view on systems to investigate, in a uniform way, under which conditions calculi that are sound and complete with respect to behavioral equivalence can be extended to a coarser coalgebraic language equivalence, which arises from a generalized powerset construction that determinizes coalgebras. We show that soundness and completeness are established by proving that expressions modulo axioms of a calculus form the rational fixpoint of the given type functor. Our main result is that the rational fixpoint of the functor FT, where T is a monad describing the branching of the systems (e.g., non-determinism, weights, probability, etc.), has as a quotient the rational fixpoint of the determinized type functor F, a lifting of F to the category of T -algebras. We apply our framework to the concrete example of weighted automata, for which we present a new sound and complete calculus for weighted language equivalence. As a special case, we obtain nondeterministic automata in which we recover Rabinovich's sound and complete calculus for language equivalence.", acknowledgement = ack-nhfb, articleno = "7", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Kartzow:2013:FOL, author = "Alexander Kartzow", title = "First-Order Logic on Higher-Order Nested Pushdown Trees", journal = j-TOCL, volume = "14", number = "2", pages = "8:1--8:??", month = jun, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2480759.2480760", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Jun 17 17:37:05 MDT 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We introduce a new hierarchy of higher-order nested pushdown trees generalising Alur et al.'s concept of nested pushdown trees. Nested pushdown trees are useful representations of control flows in the verification of programs with recursive calls of first-order functions. Higher-order nested pushdown trees are expansions of unfoldings of graphs generated by higher-order pushdown systems. Moreover, the class of nested pushdown trees of level n is uniformly first-order interpretable in the class of collapsible pushdown graphs of level n + 1. The relationship between the class of higher-order pushdown graphs and the class of collapsible higher-order pushdown graphs is not very well understood. We hope that the further study of the nested pushdown tree hierarchy leads to a better understanding of these two hierarchies. In this article, we are concerned with the first-order model checking problem on higher-order nested pushdown trees. We show that the first-order model checking on the first two levels of this hierarchy is decidable. Moreover, we obtain an alternating 2-EXPTIME algorithm for the class of nested pushdown trees of level 1. The proof technique involves a pseudo-local analysis of strategies in the Ehrenfeucht-Fra{\"\i}ss{\'e} games on two identical copies of a nested pushdown tree. Ordinary locality arguments in the spirit of Gaifman's lemma do not apply here because nested pushdown trees tend to have small diameters. We introduce the notion of relevant ancestors which provide a sufficient description of the FO$_k$ -type of each element in a higher-order nested pushdown tree. The local analysis of these ancestors allows us to prove the existence of restricted winning strategies in the Ehrenfeucht-Fra{\"\i}ss{\'e} game. These strategies are then used to create a first-order model checking algorithm.", acknowledgement = ack-nhfb, articleno = "8", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Gastin:2013:FSA, author = "Paul Gastin and Nathalie Sznajder", title = "Fair Synthesis for Asynchronous Distributed Systems", journal = j-TOCL, volume = "14", number = "2", pages = "9:1--9:??", month = jun, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2480759.2480761", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Jun 17 17:37:05 MDT 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We study the synthesis problem in an asynchronous distributed setting: a finite set of processes interact locally with an uncontrollable environment and communicate with each other by sending signals --- actions controlled by a sender process and that are immediately received by the target process. The fair synthesis problem is to come up with a local strategy for each process such that the resulting fair behaviors of the system meet a given specification. We consider external specifications satisfying some natural closure properties related to the architecture. We present this new setting for studying the fair synthesis problem for distributed systems, and give decidability results for the subclass of networks where communications happen through a strongly connected graph. We claim that this framework for distributed synthesis is natural, convenient and avoids most of the usual sources of undecidability for the synthesis problem. Hence, it may open the way to a decidable theory of distributed synthesis.", acknowledgement = ack-nhfb, articleno = "9", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Shakarian:2013:UGA, author = "Paulo Shakarian and Matthias Broecheler and V. S. Subrahmanian and Cristian Molinaro", title = "Using Generalized Annotated Programs to Solve Social Network Diffusion Optimization Problems", journal = j-TOCL, volume = "14", number = "2", pages = "10:1--10:??", month = jun, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2480759.2480762", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Jun 17 17:37:05 MDT 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "There has been extensive work in many different fields on how phenomena of interest (e.g., diseases, innovation, product adoption) ``diffuse'' through a social network. As social networks increasingly become a fabric of society, there is a need to make ``optimal'' decisions with respect to an observed model of diffusion. For example, in epidemiology, officials want to find a set of k individuals in a social network which, if treated, would minimize spread of a disease. In marketing, campaign managers try to identify a set of k customers that, if given a free sample, would generate maximal ``buzz'' about the product. In this article, we first show that the well-known Generalized Annotated Program (GAP) paradigm can be used to express many existing diffusion models. We then define a class of problems called Social Network Diffusion Optimization Problems (SNDOPs). SNDOPs have four parts: (i) a diffusion model expressed as a GAP, (ii) an objective function we want to optimize with respect to a given diffusion model, (iii) an integer k {$>$} 0 describing resources (e.g., medication) that can be placed at nodes, (iv) a logical condition VC that governs which nodes can have a resource (e.g., only children above the age of 5 can be treated with a given medication). We study the computational complexity of SNDOPs and show both NP-completeness results as well as results on complexity of approximation. We then develop an exact and a heuristic algorithm to solve a large class of SNDOP problems and show that our GREEDY-SNDOPs algorithm achieves the best possible approximation ratio that a polynomial algorithm can achieve (unless P = NP ). We conclude with a prototype experimental implementation to solve SNDOPs that looks at a real-world Wikipedia dataset consisting of over 103,000 edges.", acknowledgement = ack-nhfb, articleno = "10", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Echenim:2013:ISN, author = "Mnacho Echenim and Nicolas Peltier", title = "Instantiation Schemes for Nested Theories", journal = j-TOCL, volume = "14", number = "2", pages = "11:1--11:??", month = jun, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2480759.2480763", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Jun 17 17:37:05 MDT 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "This article investigates under which conditions instantiation-based proof procedures can be combined in a nested way, in order to mechanically construct new instantiation procedures for richer theories. Interesting applications in the field of verification are emphasized, particularly for handling extensions of the theory of arrays.", acknowledgement = ack-nhfb, articleno = "11", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Simari:2013:PAQ, author = "Gerardo I. Simari and John P. Dickerson and Amy Sliva and V. S. Subrahmanian", title = "Parallel Abductive Query Answering in Probabilistic Logic Programs", journal = j-TOCL, volume = "14", number = "2", pages = "12:1--12:??", month = jun, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2480759.2480764", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Jun 17 17:37:05 MDT 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Action-probabilistic logic programs ( ap -programs) are a class of probabilistic logic programs that have been extensively used during the last few years for modeling behaviors of entities. Rules in ap -programs have the form ``If the environment in which entity E operates satisfies certain conditions, then the probability that E will take some action A is between L and U ''. Given an ap -program, we are interested in trying to change the environment, subject to some constraints, so that the probability that entity E takes some action (or combination of actions) is maximized. This is called the Basic Abductive Query Answering Problem (BAQA). We first formally define and study the complexity of BAQA, and then go on to provide an exact (exponential time) algorithm to solve it, followed by more efficient algorithms for specific subclasses of the problem. We also develop appropriate heuristics to solve BAQA efficiently. The second problem, called the Cost-based Query Answering (CBQA) problem checks to see if there is some way of achieving a desired action (or set of actions) with a probability exceeding a threshold, given certain costs. We first formally define and study an exact (intractable) approach to CBQA, and then go on to propose a more efficient algorithm for a specific subclass of ap -programs that builds on the results for the basic version of this problem. We also develop the first algorithms for parallel evaluation of CBQA. We conclude with an extensive report on experimental evaluations performed over prototype implementations of the algorithms developed for both BAQA and CBQA, showing that our parallel algorithms work well in practice.", acknowledgement = ack-nhfb, articleno = "12", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Kontchakov:2013:TLC, author = "Roman Kontchakov and Yavor Nenov and Ian Pratt-Hartmann and Michael Zakharyaschev", title = "Topological Logics with Connectedness over {Euclidean} Spaces", journal = j-TOCL, volume = "14", number = "2", pages = "13:1--13:??", month = jun, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2480759.2480765", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Jun 17 17:37:05 MDT 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We consider the quantifier-free languages, Bc and Bc ${}^\circ $, obtained by augmenting the signature of Boolean algebras with a unary predicate representing, respectively, the property of being connected, and the property of having a connected interior. These languages are interpreted over the regular closed sets of R$^n$ ( n {$>$}= 2) and, additionally, over the regular closed semilinear sets of R$^n$. The resulting logics are examples of formalisms that have recently been proposed in the Artificial Intelligence literature under the rubric Qualitative Spatial Reasoning. We prove that the satisfiability problem for Bc is undecidable over the regular closed semilinear sets in all dimensions greater than 1, and that the satisfiability problem for Bc and Bc ${}^\circ $ is undecidable over both the regular closed sets and the regular closed semilinear sets in the Euclidean plane. However, we also prove that the satisfiability problem for Bc ${}^\circ $ is NP-complete over the regular closed sets in all dimensions greater than 2, while the corresponding problem for the regular closed semilinear sets is ExpTime-complete. Our results show, in particular, that spatial reasoning is much harder over Euclidean spaces than over arbitrary topological spaces.", acknowledgement = ack-nhfb, articleno = "13", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Delgrande:2013:MTA, author = "James Delgrande and Torsten Schaub and Hans Tompits and Stefan Woltran", title = "A Model-Theoretic Approach to Belief Change in Answer Set Programming", journal = j-TOCL, volume = "14", number = "2", pages = "14:1--14:??", month = jun, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2480759.2480766", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Jun 17 17:37:05 MDT 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We address the problem of belief change in (nonmonotonic) logic programming under answer set semantics. Our formal techniques are analogous to those of distance-based belief revision in propositional logic. In particular, we build upon the model theory of logic programs furnished by SE interpretations, where an SE interpretation is a model of a logic program in the same way that a classical interpretation is a model of a propositional formula. Hence we extend techniques from the area of belief revision based on distance between models to belief change in logic programs. We first consider belief revision: for logic programs P and Q, the goal is to determine a program R that corresponds to the revision of P by Q, denoted P * Q. We investigate several operators, including (logic program) expansion and two revision operators based on the distance between the SE models of logic programs. It proves to be the case that expansion is an interesting operator in its own right, unlike in classical belief revision where it is relatively uninteresting. Expansion and revision are shown to satisfy a suite of interesting properties; in particular, our revision operators satisfy all or nearly all of the AGM postulates for revision. We next consider approaches for merging a set of logic programs, P$_1$, ..., P$_n$. Again, our formal techniques are based on notions of relative distance between the SE models of the logic programs. Two approaches are examined. The first informally selects for each program P$_i$ those models of P$_i$ that vary the least from models of the other programs. The second approach informally selects those models of a program P$_0$ that are closest to the models of programs P$_1$, ..., P$_n$. In this case, P$_0$ can be thought of as a set of database integrity constraints. We examine these operators with regards to how they satisfy relevant postulate sets. Last, we present encodings for computing the revision as well as the merging of logic programs within the same logic programming framework. This gives rise to a direct implementation of our approach in terms of off-the-shelf answer set solvers. These encodings also reflect the fact that our change operators do not increase the complexity of the base formalism.", acknowledgement = ack-nhfb, articleno = "14", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Gebser:2013:TCL, author = "Martin Gebser and Torsten Schaub", title = "Tableau Calculi for Logic Programs under Answer Set Semantics", journal = j-TOCL, volume = "14", number = "2", pages = "15:1--15:??", month = jun, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2480759.2480767", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Jun 17 17:37:05 MDT 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We introduce formal proof systems based on tableau methods for analyzing computations in Answer Set Programming (ASP). Our approach furnishes fine-grained instruments for characterizing operations as well as strategies of ASP solvers. The granularity is detailed enough to capture a variety of propagation and choice methods of algorithms used for ASP solving, also incorporating SAT-based and conflict-driven learning approaches to some extent. This provides us with a uniform setting for identifying and comparing fundamental properties of ASP solving approaches. In particular, we investigate their proof complexities and show that the run-times of best-case computations can vary exponentially between different existing ASP solvers. Apart from providing a framework for comparing ASP solving approaches, our characterizations also contribute to their understanding by pinning down the constitutive atomic operations. Furthermore, our framework is flexible enough to integrate new inference patterns, and so to study their relation to existing ones. To this end, we generalize our approach and provide an extensible basis aiming at a modular incorporation of additional language constructs. This is exemplified by augmenting our basic tableau methods with cardinality constraints and disjunctions.", acknowledgement = ack-nhfb, articleno = "15", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Alferes:2013:QDP, author = "Jos{\'e} J{\'u}lio Alferes and Matthias Knorr and Terrance Swift", title = "Query-Driven Procedures for Hybrid {MKNF} Knowledge Bases", journal = j-TOCL, volume = "14", number = "2", pages = "16:1--16:??", month = jun, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2480759.2480768", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Jun 17 17:37:05 MDT 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Hybrid MKNF knowledge bases are one of the most prominent tightly integrated combinations of open-world ontology languages with closed-world (nonmonotonic) rule paradigms. Based on the logic of minimal knowledge and negation as failure (MKNF), the definition of Hybrid MKNF is parametric on the description logic (DL) underlying the ontology language, in the sense that nonmonotonic rules can extend any decidable DL language. Two related semantics have been defined for Hybrid MKNF: one that is based on the Stable Model Semantics for logic programs and one on the Well-Founded Semantics (WFS). Under WFS, the definition of Hybrid MKNF relies on a bottom-up computation that has polynomial data complexity whenever the DL language is tractable. Here we define a general query-driven procedure for Hybrid MKNF that is sound with respect to the stable model-based semantics, and sound and complete with respect to its WFS variant. This procedure is able to answer a slightly restricted form of conjunctive queries, and is based on tabled rule evaluation extended with an external oracle that captures reasoning within the ontology. Such an (abstract) oracle receives as input a query along with knowledge already derived, and replies with a (possibly empty) set of atoms, defined in the rules, whose truth would suffice to prove the initial query. With appropriate assumptions on the complexity of the abstract oracle, the general procedure maintains the data complexity of the WFS for Hybrid MKNF knowledge bases. To illustrate this approach, we provide a concrete oracle for EL$^+$, a fragment of the lightweight DL EL$^{++}$. Such an oracle has practical use, as EL$^{++}$ is the language underlying OWL 2 EL, which is part of the W3C recommendations for the Semantic Web, and is tractable for reasoning tasks such as subsumption. We show that query-driven Hybrid MKNF preserves polynomial data complexity when using the EL$^+$ oracle and WFS.", acknowledgement = ack-nhfb, articleno = "16", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Wittocx:2013:CPF, author = "Johan Wittocx and Marc Denecker and Maurice Bruynooghe", title = "Constraint Propagation for First-Order Logic and Inductive Definitions", journal = j-TOCL, volume = "14", number = "3", pages = "17:1--17:??", month = aug, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2499937.2499938", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Aug 28 17:07:40 MDT 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In Constraint Programming, constraint propagation is a basic component of constraint satisfaction solvers. Here we study constraint propagation as a basic form of inference in the context of first-order logic (FO) and extensions with inductive definitions (FO(ID)) and aggregates (FO(AGG)). In a first, semantic approach, a theory of propagators and constraint propagation is developed for theories in the context of three-valued interpretations. We present an algorithm with polynomial-time data complexity. We show that constraint propagation in this manner can be represented by a datalog program. In a second, symbolic approach, the semantic algorithm is lifted to a constraint propagation algorithm in symbolic structures, symbolic representations of classes of structures. The third part of the article is an overview of existing and potential applications of constraint propagation for model generation, grounding, interactive search problems, approximate methods for $ \exists \forall $ SO problems, and approximate query answering in incomplete databases.", acknowledgement = ack-nhfb, articleno = "17", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Praveen:2013:DTH, author = "M. Praveen", title = "Does Treewidth Help in Modal Satisfiability?", journal = j-TOCL, volume = "14", number = "3", pages = "18:1--18:??", month = aug, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2499937.2499939", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Aug 28 17:07:40 MDT 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Many tractable algorithms for solving the Constraint Satisfaction Problem ( Csp) have been developed using the notion of the treewidth of some graph derived from the input Csp instance. In particular, the incidence graph of the Csp instance is one such graph. We introduce the notion of an incidence graph for modal logic formulas in a certain normal form. We investigate the parameterized complexity of modal satisfiability with the modal depth of the formula and the treewidth of the incidence graph as parameters. For various combinations of Euclidean, reflexive, symmetric, and transitive models, we show either that modal satisfiability is Fixed Parameter Tractable (Fpt), or that it is W[1]-hard. In particular, modal satisfiability in general models is Fpt, while it is W[1]-hard in transitive models. As might be expected, modal satisfiability in transitive and Euclidean models is Fpt.", acknowledgement = ack-nhfb, articleno = "18", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Tan:2013:GRP, author = "Tony Tan", title = "Graph Reachability and Pebble Automata over Infinite Alphabets", journal = j-TOCL, volume = "14", number = "3", pages = "19:1--19:??", month = aug, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2499937.2499940", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Aug 28 17:07:40 MDT 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Let D denote an infinite alphabet --- a set that consists of infinitely many symbols. A word $ w = a_0 b_0 a_1 b_1 \cdot \cdot \cdot a_n b_n $ of even length over {$D$} can be viewed as a directed graph {$ G_w $} whose vertices are the symbols that appear in $w$, and the edges are $ (a_0, b_0), (a_1, b_1), \ldots {}, (a_n, b_n) $. For a positive integer $m$, define a language {$ R_m $} such that a word {$ w = a_0 b_0 \cdot \cdot \cdot a_n b_n \in R_m $} if and only if there is a path in the graph {$ G_w $} of length $ \leq m $ from the vertex $ a_0 $ to the vertex $ b_n $. We establish the following hierarchy theorem for pebble automata over infinite alphabet. For every positive integer $k$, (i) there exists a $k$-pebble automaton that accepts the language {$ R_{2k - 1} $}; (ii) there is no $k$-pebble automaton that accepts the language {$ R_{2k + 1 - 2} $}. Using this fact, we establish the following main results in this article: (a) a strict hierarchy of the pebble automata languages based on the number of pebbles; (b) the separation of monadic second order logic from the pebble automata languages; (c) the separation of one-way deterministic register automata languages from pebble automata languages.", acknowledgement = ack-nhfb, articleno = "19", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Beyersdorff:2013:PCD, author = "Olaf Beyersdorff and Nicola Galesi and Massimo Lauria", title = "Parameterized Complexity of {DPLL} Search Procedures", journal = j-TOCL, volume = "14", number = "3", pages = "20:1--20:??", month = aug, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2499937.2499941", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Aug 28 17:07:40 MDT 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We study the performance of DPLL algorithms on parameterized problems. In particular, we investigate how difficult it is to decide whether small solutions exist for satisfiability and other combinatorial problems. For this purpose we develop a Prover-Delayer game that models the running time of DPLL procedures and we establish an information-theoretic method to obtain lower bounds to the running time of parameterized DPLL procedures. We illustrate this technique by showing lower bounds to the parameterized pigeonhole principle and to the ordering principle. As our main application we study the DPLL procedure for the problem of deciding whether a graph has a small clique. We show that proving the absence of a k -clique requires {$ n^{\Omega (k)} $} steps for a nontrivial distribution of graphs close to the critical threshold. For the restricted case of tree-like Parameterized Resolution, this result answers a question asked by Beyersdorff et al. [2012] of understanding the Resolution complexity of this family of formulas.", acknowledgement = ack-nhfb, articleno = "20", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Charalambidis:2013:EHO, author = "Angelos Charalambidis and Konstantinos Handjopoulos and Panagiotis Rondogiannis and William W. Wadge", title = "Extensional Higher-Order Logic Programming", journal = j-TOCL, volume = "14", number = "3", pages = "21:1--21:??", month = aug, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2499937.2499942", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Aug 28 17:07:40 MDT 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We propose a purely extensional semantics for higher-order logic programming. In this semantics program predicates denote sets of ordered tuples, and two predicates are equal iff they are equal as sets. Moreover, every program has a unique minimum Herbrand model which is the greatest lower bound of all Herbrand models of the program and the least fixed-point of an immediate consequence operator. We also propose an SLD-resolution proof system which is proven sound and complete with respect to the minimum Herbrand model semantics. In other words, we provide a purely extensional theoretical framework for higher-order logic programming which generalizes the familiar theory of classical (first-order) logic programming.", acknowledgement = ack-nhfb, articleno = "21", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Albert:2013:IRU, author = "Elvira Albert and Samir Genaim and Abu Naser Masud", title = "On the Inference of Resource Usage Upper and Lower Bounds", journal = j-TOCL, volume = "14", number = "3", pages = "22:1--22:??", month = aug, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2499937.2499943", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Aug 28 17:07:40 MDT 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Cost analysis aims at determining the amount of resources required to run a program in terms of its input data sizes. The most challenging step is to infer the cost of executing the loops in the program. This requires bounding the number of iterations of each loop and finding tight bounds for the cost of each of its iterations. This article presents a novel approach to infer upper and lower bounds from cost relations. These relations are an extended form of standard recurrence equations that can be nondeterministic, contain inexact size constraints and have multiple arguments that increase and/or decrease. We propose novel techniques to automatically transform cost relations into worst-case and best-case deterministic one-argument recurrence relations. The solution of each recursive relation provides a precise upper-bound and lower-bound for executing a corresponding loop in the program. Importantly, since the approach is developed at the level of the cost equations, our techniques are programming language independent.", acknowledgement = ack-nhfb, articleno = "22", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Sietsma:2013:CKE, author = "Floor Sietsma and Krzysztof R. Apt", title = "Common Knowledge in Email Exchanges", journal = j-TOCL, volume = "14", number = "3", pages = "23:1--23:??", month = aug, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2499937.2499944", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Aug 28 17:07:40 MDT 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We consider a framework in which a group of agents communicates by means of emails, with the possibility of replies, forwards and blind carbon copies (BCC). We study the epistemic consequences of such email exchanges by introducing an appropriate epistemic language and semantics. This allows us to find out what agents learn from the emails they receive and to determine when a group of agents acquires common knowledge of the fact that an email was sent. We also show that in our framework from the epistemic point of view the BCC feature of emails cannot be simulated using messages without BCC recipients.", acknowledgement = ack-nhfb, articleno = "23", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Herzig:2013:PUO, author = "Andreas Herzig and Jerome Lang and Pierre Marquis", title = "Propositional Update Operators Based on Formula\slash Literal Dependence", journal = j-TOCL, volume = "14", number = "3", pages = "24:1--24:??", month = aug, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2499937.2499945", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Aug 28 17:07:40 MDT 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We present and study a general family of belief update operators in a propositional setting. Its operators are based on formula/ literal dependence, which is more fine-grained than the notion of formula/ variable dependence that was proposed in the literature: formula/variable dependence is a particular case of formula/literal dependence. Our update operators are defined according to the ``forget-then-conjoin'' scheme: updating a belief base by an input formula consists in first forgetting in the base every literal on which the input formula has a negative influence, and then conjoining the resulting base with the input formula. The operators of our family differ by the underlying notion of formula/literal dependence, which may be defined syntactically or semantically, and which may or may not exploit further information like known persistent literals and pre-set dependencies. We argue that this allows to handle the frame problem and the ramification problem in a more appropriate way. We evaluate the update operators of our family w.r.t. two important dimensions: the logical dimension, by checking the status of the Katsuno-Mendelzon postulates for update, and the computational dimension, by identifying the complexity of a number of decision problems (including model checking, consistency and inference), both in the general case and in some restricted cases, as well as by studying compactability issues. It follows that several operators of our family are interesting alternatives to previous belief update operators.", acknowledgement = ack-nhfb, articleno = "24", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Kazana:2013:EMS, author = "Wojciech Kazana and Luc Segoufin", title = "Enumeration of monadic second-order queries on trees", journal = j-TOCL, volume = "14", number = "4", pages = "25:1--25:??", month = nov, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2528928", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Dec 3 18:27:46 MST 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We consider the enumeration problem of Monadic Second-Order (MSO) queries with first-order free variables over trees. In Bagan [2006] it was shown that this problem is in CONSTANT-DELAY$_{lin}$. An enumeration problem belongs to CONSTANT-DELAY$_{lin}$ if for an input structure of size n it can be solved by:\par --- an $ O(n)$ precomputation phase building an index structure,\par --- followed by a phase enumerating the answers with no repetition and a constant delay between two consecutive outputs.\par In this article we give a different proof of this result based on the deterministic factorization forest decomposition theorem of Colcombet [2007].", acknowledgement = ack-nhfb, articleno = "25", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Heras:2013:CPH, author = "J{\'o}nathan Heras and Thierry Coquand and Anders M{\"o}rtberg and Vincent Siles", title = "Computing persistent homology within {Coq\slash SSReflect}", journal = j-TOCL, volume = "14", number = "4", pages = "26:1--26:??", month = nov, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2528929", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Dec 3 18:27:46 MST 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Persistent homology is one of the most active branches of computational algebraic topology with applications in several contexts such as optical character recognition or analysis of point cloud data. In this article, we report on the formal development of certified programs to compute persistent Betti numbers, an instrumental tool of persistent homology, using the C oq proof assistant together with the SSReflect extension. To this aim it has been necessary to formalize the underlying mathematical theory of these algorithms. This is another example showing that interactive theorem provers have reached a point where they are mature enough to tackle the formalization of nontrivial mathematical theories.", acknowledgement = ack-nhfb, articleno = "26", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Lahav:2013:USF, author = "Ori Lahav and Arnon Avron", title = "A unified semantic framework for fully structural propositional sequent systems", journal = j-TOCL, volume = "14", number = "4", pages = "27:1--27:??", month = nov, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2528930", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Dec 3 18:27:46 MST 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We identify a large family of fully structural propositional sequent systems, which we call basic systems. We present a general uniform method for providing (potentially, nondeterministic) strongly sound and complete Kripke-style semantics, which is applicable for every system of this family. In addition, this method can also be applied when: (i) some formulas are not allowed to appear in derivations, (ii) some formulas are not allowed to serve as cut formulas, and (iii) some instances of the identity axiom are not allowed to be used. This naturally leads to new semantic characterizations of analyticity (global subformula property), cut admissibility and axiom expansion in basic systems. We provide a large variety of examples showing that many soundness and completeness theorems for different sequent systems, as well as analyticity, cut admissibility, and axiom expansion results, easily follow using the general method of this article.", acknowledgement = ack-nhfb, articleno = "27", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Gaintzarain:2013:LFM, author = "Jose Gaintzarain and Paqui Lucio", title = "Logical foundations for more expressive declarative temporal logic programming languages", journal = j-TOCL, volume = "14", number = "4", pages = "28:1--28:??", month = nov, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2528931", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Dec 3 18:27:46 MST 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In this article, we present a declarative propositional temporal logic programming language called TeDiLog that is a combination of the temporal and disjunctive paradigms in logic programming. TeDiLog is, syntactically, a sublanguage of the well-known Propositional Linear-time Temporal Logic (PLTL). TeDiLog allows both eventualities and always-formulas to occur in clause heads and also in clause bodies. To the best of our knowledge, TeDiLog is the first declarative temporal logic programming language that achieves this high degree of expressiveness. We establish the logical foundations of our proposal by formally defining operational and logical semantics for TeDiLog and by proving their equivalence. The operational semantics of TeDiLog relies on a restriction of the invariant-free temporal resolution procedure for PLTL that was introduced by Gaintzarain et al. in [2013]. We define a fixpoint semantics that captures the reverse (bottom-up) operational mechanism and prove its equivalence with the logical semantics. We also provide illustrative examples and comparison with other proposals.", acknowledgement = ack-nhfb, articleno = "28", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Danvy:2013:TST, author = "Olivier Danvy and Ian Zerny", title = "Three syntactic theories for combinatory graph reduction", journal = j-TOCL, volume = "14", number = "4", pages = "29:1--29:??", month = nov, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2528932", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Dec 3 18:27:46 MST 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We present a purely syntactic theory of graph reduction for the canonical combinators S, K, and I, where graph vertices are represented with evaluation contexts and let expressions. We express this first syntactic theory as a storeless reduction semantics of combinatory terms. We then factor out the introduction of let expressions to denote as many graph vertices as possible upfront instead of on demand. The factored terms can be interpreted as term graphs in the sense of Barendregt et al. We express this second syntactic theory, which we prove equivalent to the first, as a storeless reduction semantics of combinatory term graphs. We then recast let bindings as bindings in a global store, thus shifting, in Strachey's words, from denotable entities to storable entities. The store-based terms can still be interpreted as term graphs. We express this third syntactic theory, which we prove equivalent to the second, as a store-based reduction semantics of combinatory term graphs. We then refocus this store-based reduction semantics into a store-based abstract machine. The architecture of this store-based abstract machine coincides with that of Turner's original reduction machine. The three syntactic theories presented here therefore properly account for combinatory graph reduction As We Know It. These three syntactic theories scale to handling the Y combinator. This article therefore illustrates the scientific consensus of theoreticians and implementors about graph reduction: it is the same combinatory elephant.", acknowledgement = ack-nhfb, articleno = "29", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bodirsky:2013:CST, author = "Manuel Bodirsky and H. Dugald Macpherson and Johan Thapper", title = "Constraint satisfaction tractability from semi-lattice operations on infinite sets", journal = j-TOCL, volume = "14", number = "4", pages = "30:1--30:??", month = nov, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2528933", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Dec 3 18:27:46 MST 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "A famous result by Jeavons, Cohen, and Gyssens shows that every Constraint Satisfaction Problem (CSP) where the constraints are preserved by a semi-lattice operation can be solved in polynomial time. This is one of the basic facts for the so-called universal algebraic approach to a systematic theory of tractability and hardness in finite domain constraint satisfaction. Not surprisingly, the theorem of Jeavons et al. fails for arbitrary infinite domain CSPs. Many CSPs of practical interest, though, and in particular those CSPs that are motivated by qualitative reasoning calculi from artificial intelligence, can be formulated with constraint languages that are rather well-behaved from a model-theoretic point of view. In particular, the automorphism group of these constraint languages tends to be large in the sense that the number of orbits of $n$-subsets of the automorphism group is bounded by some function in $n$. In this article we present a generalization of the theorem by Jeavons et al. to infinite domain CSPs where the number of orbits of $n$-subsets grows subexponentially in $n$, and prove that preservation under a semi-lattice operation for such CSPs implies polynomial-time tractability. Unlike the result of Jeavons et al., this includes CSPs that cannot be solved by Datalog.", acknowledgement = ack-nhfb, articleno = "30", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Ketema:2013:LUB, author = "Jeroen Ketema and Jakob Grue Simonsen", title = "Least upper bounds on the size of confluence and {Church--Rosser} diagrams in term rewriting and $ \lambda $-calculus", journal = j-TOCL, volume = "14", number = "4", pages = "31:1--31:??", month = nov, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2528934", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Dec 3 18:27:46 MST 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We study confluence and the Church--Rosser property in term rewriting and $ \lambda $-calculus with explicit bounds on term sizes and reduction lengths. Given a system $R$, we are interested in the lengths of the reductions in the smallest valleys $ t \rightarrow * s ' * \leftarrow t '$ expressed as a function:\par --- for confluence a function $ {\rm vs}_R(m, n)$ where the valleys are for peaks $ t \leftarrow s \rightarrow * t '$ with $s$ of size at most $m$ and the reductions of maximum length $n$, and\par --- for the Church--Rosser property a function $ {\rm cvs}_R (m, n)$ where the valleys are for conversions $ t \leftrightarrow * t$ with $t$ and $ t'$ of size at most $m$ and the conversion of maximum length $n$.\par For confluent Term Rewriting Systems (TRSs), we prove that $ {\rm vs}_R$ is a total computable function, and for linear such systems that $ {\rm cvs}_R$ is a total computable function. Conversely, we show that every total computable function is the lower bound on the functions $ {\rm vs}_R (m, n)$ and $ {\rm cvs}_R (m, n)$ for some TRS {$R$}: In particular, we show that for every total computable function $ \varphi : N \rightarrow N$ there is a TRS $R$ with a single term $s$ such that $ {\rm vs}_R (| s |, n) \geq \varphi (n)$ and $ {\rm cvs}_R (n, n) \geq \varphi (n)$ for all n. For orthogonal TRSs $R$ we prove that there is a constant $k$ such that: (a) $ {\rm vs}_R (m, n)$ is bounded from above by a function exponential in $k$ and (b) $ {\rm cvs}_R (m, n)$ is bounded from above by a function in the fourth level of the Grzegorczyk hierarchy. Similarly, for $ \lambda $-calculus, we show that $ {\rm vs}_R(m, n)$ is bounded from above by a function in the fourth level of the Grzegorczyk hierarchy.", acknowledgement = ack-nhfb, articleno = "31", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Rabe:2013:LRL, author = "Florian Rabe and Kristina Sojakova", title = "Logical relations for a logical framework", journal = j-TOCL, volume = "14", number = "4", pages = "32:1--32:??", month = nov, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2536740.2536741", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Dec 3 18:27:46 MST 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Logical relations are a central concept used to study various higher-order type theories and occur frequently in the proofs of a wide variety of meta-theorems. Besides extending the logical relation principle to more general languages, an important research question has been how to represent and thus verify logical relation arguments in logical frameworks. We formulate a theory of logical relations for Dependent Type Theory (DTT) with \beta \eta -equality which guarantees that any valid logical relation satisfies the Basic Lemma. Our definition is syntactic and reflective in the sense that a relation at a type is represented as a DTT type family but also permits expressing certain semantic definitions. We use the Edinburgh Logical Framework (LF) incarnation of DTT and implement our notion of logical relations in the type-checker Twelf. This enables us to formalize and mechanically decide the validity of logical relation arguments. Furthermore, our implementation includes a module system so that logical relations can be built modularly. We validate our approach by formalizing and verifying several syntactic and semantic meta-theorems in Twelf. Moreover, we show how object languages encoded in DTT can inherit a notion of logical relation from the logical framework.", acknowledgement = ack-nhfb, articleno = "32", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Chen:2013:VLD, author = "Taolue Chen and Marco Diciolla and Marta Kwiatkowska and Alexandru Mereacre", title = "Verification of linear duration properties over continuous-time {Markov} chains", journal = j-TOCL, volume = "14", number = "4", pages = "33:1--33:??", month = nov, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2528935", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Dec 3 18:27:46 MST 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Stochastic modelling and algorithmic verification techniques have been proved useful in analysing and detecting unusual trends in performance and energy usage of systems such as power management controllers and wireless sensor devices. Many important properties are dependent on the cumulated time that the device spends in certain states, possibly intermittently. We study the problem of verifying continuous-time Markov Chains (CTMCs) against Linear Duration Properties (LDP), that is, properties stated as conjunctions of linear constraints over the total duration of time spent in states that satisfy a given property. We identify two classes of LDP properties, Eventuality Duration Properties (EDP) and Invariance Duration Properties (IDP), respectively referring to the reachability of a set of goal states, within a time bound; and the continuous satisfaction of a duration property over an execution path. The central question that we address is how to compute the probability of the set of infinite timed paths of the CTMC that satisfy a given LDP. We present algorithms to approximate these probabilities up to a given precision, stating their complexity and error bounds. The algorithms mainly employ an adaptation of uniformisation and the computation of volumes of multidimensional integrals under systems of linear constraints, together with different mechanisms to bound the errors.", acknowledgement = ack-nhfb, articleno = "33", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Dyckhoff:2013:APT, author = "Roy Dyckhoff and Mehrnoosh Sadrzadeh and Julien Truffaut", title = "Algebra, proof theory and applications for an intuitionistic logic of propositions, actions and adjoint modal operators", journal = j-TOCL, volume = "14", number = "4", pages = "34:1--34:??", month = nov, year = "2013", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2536740.2536742", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Dec 3 18:27:46 MST 2013", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We develop a cut-free nested sequent calculus as basis for a proof search procedure for an intuitionistic modal logic of actions and propositions. The actions act on propositions via a dynamic modality (the weakest precondition of program logics), whose left adjoint we refer to as ``update'' (the strongest postcondition ). The logic has agent-indexed adjoint pairs of epistemic modalities: the left adjoints encode agents' uncertainties and the right adjoints encode their beliefs. The rules for the ``update'' modality encode learning as a result of discarding uncertainty. We prove admissibility of Cut, and hence the soundness and completeness of the logic with respect to an algebraic semantics. We interpret the logic on epistemic scenarios that consist of honest and dishonest communication actions, add assumption rules to encode them, and prove that the calculus with the assumption rules still has the admissibility results. We apply the calculus to encode (and allow reasoning about) the classic epistemic puzzles of dirty children (a.k.a. ``muddy children'') and drinking logicians and some versions with dishonesty or noise; we also give an application where the actions are movements of a robot rather than announcements.", acknowledgement = ack-nhfb, articleno = "34", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bauer:2014:PCF, author = "Matthew S. Bauer", title = "A {PSPACE-complete} first-order fragment of computability logic", journal = j-TOCL, volume = "15", number = "1", pages = "1:1--1:??", month = feb, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2559949", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Feb 28 17:01:18 MST 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In a recently launched research program for developing logic as a formal theory of (interactive) computability, several very interesting logics have been introduced and axiomatized. These fragments of the larger Computability Logic aim not only to describe what can be computed, but also provide a mechanism for extracting computational algorithms from proofs. Among the most expressive and fundamental of these is CL4, known to be (constructively) sound and complete with respect to the underlying computational semantics. Furthermore, the $\forall$, $\exists$-free fragment of CL4 was shown to be decidable in polynomial space. The present work extends this result and proves that this fragment is, in fact, PSPACE-complete.", acknowledgement = ack-nhfb, articleno = "1", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Beckmann:2014:IWL, author = "Arnold Beckmann and Samuel R. Buss", title = "Improved witnessing and local improvement principles for second-order bounded arithmetic", journal = j-TOCL, volume = "15", number = "1", pages = "2:1--2:??", month = feb, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2559950", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Feb 28 17:01:18 MST 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "This article concerns the second-order systems $U^1_2$ and $V^1_2$ of bounded arithmetic, which have proof-theoretic strengths corresponding to polynomial-space and exponential-time computation. We formulate improved witnessing theorems for these two theories by using $S^1_2$ as a base theory for proving the correctness of the polynomial-space or exponential-time witnessing functions. We develop the theory of nondeterministic polynomial-space computation, including Savitch's theorem, in $U^1_2$. Kolodziejczyk et al. [2011] have introduced local improvement properties to characterize the provably total NP functions of these second-order theories. We show that the strengths of their local improvement principles over $U^1_2$ and $V^1_2$ depend primarily on the topology of the underlying graph, not the number of rounds in the local improvement games. The theory $U^1_2$ proves the local improvement principle for linear graphs even without restricting to logarithmically many rounds. The local improvement principle for grid graphs with only logarithmically-many rounds is complete for the provably total NP search problems of $V^1_2$. Related results are obtained for local improvement principles with one improvement round and for local improvement over rectangular grids.", acknowledgement = ack-nhfb, articleno = "2", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bonchi:2014:ACD, author = "Filippo Bonchi and Marcello M. Bonsangue and Helle H. Hansen and Prakash Panangaden and Jan J. M. M. Rutten and Alexandra Silva", title = "Algebra-coalgebra duality in {Brzozowski}'s minimization algorithm", journal = j-TOCL, volume = "15", number = "1", pages = "3:1--3:??", month = feb, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2490818", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Feb 28 17:01:18 MST 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We give a new presentation of Brzozowski's algorithm to minimize finite automata using elementary facts from universal algebra and coalgebra and building on earlier work by Arbib and Manes on a categorical presentation of Kalman duality between reachability and observability. This leads to a simple proof of its correctness and opens the door to further generalizations. Notably, we derive algorithms to obtain minimal language equivalent automata from Moore nondeterministic and weighted automata.", acknowledgement = ack-nhfb, articleno = "3", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Fernandez-Duque:2014:NFA, author = "David Fern{\'a}ndez-Duque", title = "Non-finite axiomatizability of dynamic topological logic", journal = j-TOCL, volume = "15", number = "1", pages = "4:1--4:??", month = feb, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2489334", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Feb 28 17:01:18 MST 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Dynamic topological logic (DTL) is a polymodal logic designed for reasoning about dynamic topological systems. These are pairs $ \langle X, f \rangle $, where $X$ is a topological space and $ f : X \to X $ is continuous. DTL uses a language L which combines the topological S4 modality $ \Square $ with temporal operators from linear temporal logic.\par Recently, we gave a sound and complete axiomatization DTL$^*$ for an extension of the logic to the language L$^*$, where $ \Diamond $ is allowed to act on finite sets of formulas and is interpreted as a tangled closure operator. No complete axiomatization is known in the language L, although one proof system, which we shall call KM, was conjectured to be complete by Kremer and Mints.\par In this article, we show that given any language L' such that L \subseteq L' \subseteq L$^*$, the set of valid formulas of L' is not finitely axiomatizable. It follows, in particular, that KM is incomplete.", acknowledgement = ack-nhfb, articleno = "4", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bruttomesso:2014:QFI, author = "Roberto Bruttomesso and Silvio Ghilardi and Silvio Ranise", title = "Quantifier-free interpolation in combinations of equality interpolating theories", journal = j-TOCL, volume = "15", number = "1", pages = "5:1--5:??", month = feb, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2490253", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Feb 28 17:01:18 MST 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The use of interpolants in verification is gaining more and more importance. Since theories used in applications are usually obtained as (disjoint) combinations of simpler theories, it is important to modularly reuse interpolation algorithms for the component theories. We show that a sufficient and necessary condition to do this for quantifier-free interpolation is that the component theories have the strong ( sub -) amalgamation property. Then, we provide an equivalent syntactic characterization and show that such characterization covers most theories commonly employed in verification. Finally, we design a combined quantifier-free interpolation algorithm capable of handling both convex and nonconvex theories; this algorithm subsumes and extends most existing work on combined interpolation.", acknowledgement = ack-nhfb, articleno = "5", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Atserias:2014:DLB, author = "Albert Atserias and Anuj Dawar", title = "Degree lower bounds of tower-type for approximating formulas with parity quantifiers", journal = j-TOCL, volume = "15", number = "1", pages = "6:1--6:??", month = feb, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2559948", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Feb 28 17:01:18 MST 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Kolaitis and Kopparty have shown that for any first-order formula with parity quantifiers over the language of graphs, there is a family of multivariate polynomials of constant-degree that agree with the formula on all but a $ 2^{- \Omega (n)} $-fraction of the graphs with n vertices. The proof bounds the degree of the polynomials by a tower of exponentials whose height is the nesting depth of parity quantifiers in the formula. We show that this tower-type dependence is necessary. We build a family of formulas of depth $q$ whose approximating polynomials must have degree bounded from below by a tower of exponentials of height proportional to $q$. Our proof has two main parts. First, we adapt and extend the results by Kolaitis and Kopparty that describe the joint distribution of the parities of the numbers of copies of small subgraphs in a random graph to the setting of graphs of growing size. Second, we analyze a variant of Karp's graph canonical labeling algorithm and exploit its massive parallelism to get a formula of low depth that defines an almost canonical pre-order on a random graph.", acknowledgement = ack-nhfb, articleno = "6", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Schmidt:2014:UTD, author = "Renate A. Schmidt and Dmitry Tishkovsky", title = "Using tableau to decide description logics with full role negation and identity", journal = j-TOCL, volume = "15", number = "1", pages = "7:1--7:??", month = feb, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2559947", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Feb 28 17:01:18 MST 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "This article presents a tableau approach for deciding expressive description logics with full role negation and role identity. We consider the description logic ALBO$^{id}$, which is ALC extended with the Boolean role operators, inverse of roles, the identity role, and includes full support for individuals and singleton concepts. ALBO$^{id}$ is expressively equivalent to the two-variable fragment of first-order logic with equality and subsumes Boolean modal logic. In this article, we define a sound, complete, and terminating tableau calculus for ALBO$^{id}$ that provides the basis for decision procedures for this logic and all its sublogics. An important novelty of our approach is the use of a generic unrestricted blocking mechanism. Unrestricted blocking is based on equality reasoning and a conceptually simple rule, which performs case distinctions over the identity of individuals. The blocking mechanism ties the proof of termination of tableau derivations to the finite model property of ALBO$^{id}$.", acknowledgement = ack-nhfb, articleno = "7", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Tan:2014:ETV, author = "Tony Tan", title = "Extending two-variable logic on data trees with order on data values and its automata", journal = j-TOCL, volume = "15", number = "1", pages = "8:1--8:??", month = feb, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2559945", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Feb 28 17:01:18 MST 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Data trees are trees in which each node, besides carrying a label from a finite alphabet, also carries a data value from an infinite domain. They have been used as an abstraction model for reasoning tasks on XML and verification. However, most existing approaches consider the case where only equality test can be performed on the data values. In this article we study data trees in which the data values come from a linearly ordered domain, and in addition to equality test, we can test whether the data value in a node is greater than the one in another node. We introduce an automata model for them which we call ordered-data tree automata (ODTA), provide its logical characterisation, and prove that its non-emptiness problem is decidable in 3-NE xpTime. We also show that the two-variable logic on unranked data trees, studied by Bojanczyk et al. [2009], corresponds precisely to a special subclass of this automata model. Then we define a slightly weaker version of ODTA, which we call weak ODTA, and provide its logical characterisation. The complexity of the non-emptiness problem drops to NP. However, a number of existing formalisms and models studied in the literature can be captured already by weak ODTA. We also show that the definition of ODTA can be easily modified, to the case where the data values come from a tree-like partially ordered domain, such as strings.", acknowledgement = ack-nhfb, articleno = "8", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Chen:2014:CEP, author = "Hubie Chen", title = "On the complexity of existential positive queries", journal = j-TOCL, volume = "15", number = "1", pages = "9:1--9:??", month = feb, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2559946", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Feb 28 17:01:18 MST 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We systematically investigate the complexity of model checking the existential positive fragment of first-order logic. In particular, for a set of existential positive sentences, we consider model checking where the sentence is restricted to fall into the set; a natural question is then to classify which sentence sets are tractable and which are intractable. With respect to fixed-parameter tractability, we give a general theorem that reduces this classification question to the corresponding question for primitive positive logic, for a variety of representations of structures. This general theorem allows us to deduce that an existential positive sentence set having bounded arity is fixed-parameter tractable if and only if each sentence is equivalent to one in bounded-variable logic. We then use the lens of classical complexity to study these fixed-parameter tractable sentence sets. We show that such a set can be NP-complete, and consider the length needed by a translation from sentences in such a set to bounded-variable logic; we prove superpolynomial lower bounds on this length using the theory of compilability, obtaining an interesting type of formula size lower bound. Overall, the tools, concepts, and results of this article set the stage for the future consideration of the complexity of model checking on more expressive logics.", acknowledgement = ack-nhfb, articleno = "9", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Zhang:2014:RCB, author = "Lan Zhang and Ullrich Hustadt and Clare Dixon", title = "A resolution calculus for the branching-time temporal logic {CTL}", journal = j-TOCL, volume = "15", number = "1", pages = "10:1--10:??", month = feb, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2529993", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Feb 28 17:01:18 MST 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The branching-time temporal logic CTL is useful for specifying systems that change over time and involve quantification over possible futures. Here we present a resolution calculus for CTL that involves the translation of formulae to a normal form and the application of a number of resolution rules. We use indices in the normal form to represent particular paths and the application of the resolution rules is restricted dependent on an ordering and selection function to reduce the search space. We show that the translation preserves satisfiability, the calculus is sound, complete, and terminating, and consider the complexity of the calculus.", acknowledgement = ack-nhfb, articleno = "10", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Asuncion:2014:PFO, author = "Vernon Asuncion and Yan Zhang and Yi Zhou", title = "Preferred First-Order Answer Set Programs", journal = j-TOCL, volume = "15", number = "2", pages = "11:1--11:??", month = apr, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2579817", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon May 5 17:57:30 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In this article, we consider the issue of how first-order answer set programs can be extended for handling preference reasoning. To this end, we propose a progression-based preference semantics for first-order answer set programs while explicit preference relations are presented. We study essential properties of the proposed preferred answer set semantics. To understand the expressiveness of preferred first-order answer set programming, we further specify a second-order logic representation which precisely characterizes the progression-based preference semantics.", acknowledgement = ack-nhfb, articleno = "11", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Son:2014:FNU, author = "Tran Cao Son and Enrico Pontelli and Ngoc-Hieu Nguyen and Chiaki Sakama", title = "Formalizing Negotiations Using Logic Programming", journal = j-TOCL, volume = "15", number = "2", pages = "12:1--12:??", month = apr, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2526270", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon May 5 17:57:30 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The article introduces a logical framework for negotiation among dishonest agents. The framework relies on the use of abductive logic programming as a knowledge representation language for agents to deal with incomplete information and preferences. The article shows how intentionally false or inaccurate information of agents can be encoded in the agents' knowledge bases. Such disinformation can be effectively used in the process of negotiation to have desired outcomes by agents. The negotiation processes are formulated under the answer set semantics of abductive logic programming, and they enable the exploration of various strategies that agents can employ in their negotiation. A preliminary implementation has been developed using the ASP-Prolog platform.", acknowledgement = ack-nhfb, articleno = "12", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Eisner:2014:SLW, author = "Cindy Eisner and Dana Fisman and John Havlicek", title = "Safety and Liveness, Weakness and Strength, and the Underlying Topological Relations", journal = j-TOCL, volume = "15", number = "2", pages = "13:1--13:??", month = apr, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2532440", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon May 5 17:57:30 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We present a characterization that shows what it means for a formula to be a weak or strong version of another formula. We show that the weak version of a formula is not the same as Alpern and Schneider's safety component, but can be achieved by taking the closure in the Cantor topology over an augmented alphabet in which every formula is satisfiable. The resulting characterization allows us to show that the set of semantically weak formulas is exactly the set of nonpathological safety formulas. Furthermore, we use the characterization to show that the original versions of the ieee standard temporal logics psl and sva are broken, and we show that the source of the problem lies in the semantics of the sere intersection and fusion operators. Finally, we use the topological characterization to show the internal consistency of the alternative semantics adopted by the latest version of the psl standard.", acknowledgement = ack-nhfb, articleno = "13", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Feng:2014:SBQ, author = "Yuan Feng and Yuxin Deng and Mingsheng Ying", title = "Symbolic Bisimulation for Quantum Processes", journal = j-TOCL, volume = "15", number = "2", pages = "14:1--14:??", month = apr, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2579818", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon May 5 17:57:30 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "With the previous notions of bisimulation presented in the literature, to check if two quantum processes are bisimilar, we have to instantiate their free quantum variables with arbitrary quantum states, and verify the bisimilarity of the resulting configurations. This makes checking bisimilarity infeasible from an algorithmic point of view, because quantum states constitute a continuum. In this article, we introduce a symbolic operational semantics for quantum processes directly at the quantum operation level, which allows us to describe the bisimulation between quantum processes without resorting to quantum states. We show that the symbolic bisimulation defined here is equivalent to the open bisimulation for quantum processes in previous work, when strong bisimulations are considered. An algorithm for checking symbolic ground bisimilarity is presented. We also give a modal characterisation for quantum bisimilarity based on an extension of Hennessy--Milner logic to quantum processes.", acknowledgement = ack-nhfb, articleno = "14", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bollig:2014:PWA, author = "Benedikt Bollig and Paul Gastin and Benjamin Monmege and Marc Zeitoun", title = "Pebble Weighted Automata and Weighted Logics", journal = j-TOCL, volume = "15", number = "2", pages = "15:1--15:??", month = apr, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2579819", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon May 5 17:57:30 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We introduce new classes of weighted automata on words. Equipped with pebbles, they go beyond the class of recognizable formal power series: they capture weighted first-order logic enriched with a quantitative version of transitive closure. In contrast to previous work, this calculus allows for unrestricted use of existential and universal quantifications over positions of the input word. We actually consider both two-way and one-way pebble weighted automata. The latter class constrains the head of the automaton to walk left-to-right, resetting it each time a pebble is dropped. Such automata have already been considered in the Boolean setting, in the context of data words. Our main result states that two-way pebble weighted automata, one-way pebble weighted automata, and our weighted logic are expressively equivalent. We also give new logical characterizations of standard recognizable series.", acknowledgement = ack-nhfb, articleno = "15", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Chatterjee:2014:POS, author = "Krishnendu Chatterjee and Laurent Doyen", title = "Partial-Observation Stochastic Games: How to Win when Belief Fails", journal = j-TOCL, volume = "15", number = "2", pages = "16:1--16:??", month = apr, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2579821", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon May 5 17:57:30 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In two-player finite-state stochastic games of partial observation on graphs, in every state of the graph, the players simultaneously choose an action, and their joint actions determine a probability distribution over the successor states. The game is played for infinitely many rounds and thus the players construct an infinite path in the graph. We consider reachability objectives where the first player tries to ensure a target state to be visited almost-surely (i.e., with probability 1) or positively (i.e., with positive probability), no matter the strategy of the second player. We classify such games according to the information and to the power of randomization available to the players. On the basis of information, the game can be one-sided with either ( a ) player 1, or ( b ) player 2 having partial observation (and the other player has perfect observation), or two-sided with ( c ) both players having partial observation. On the basis of randomization, ( a ) the players may not be allowed to use randomization (pure strategies), or ( b ) they may choose a probability distribution over actions but the actual random choice is external and not visible to the player (actions invisible), or ( c ) they may use full randomization. Our main results for pure strategies are as follows: (1) For one-sided games with player 2 having perfect observation we show that (in contrast to full randomized strategies) belief-based (subset-construction based) strategies are not sufficient, and we present an exponential upper bound on memory both for almost-sure and positive winning strategies; we show that the problem of deciding the existence of almost-sure and positive winning strategies for player 1 is EXPTIME-complete and present symbolic algorithms that avoid the explicit exponential construction. (2) For one-sided games with player 1 having perfect observation we show that nonelementary memory is both necessary and sufficient for both almost-sure and positive winning strategies. (3) We show that for the general (two-sided) case finite-memory strategies are sufficient for both positive and almost-sure winning, and at least nonelementary memory is required. We establish the equivalence of the almost-sure winning problems for pure strategies and for randomized strategies with actions invisible. Our equivalence result exhibit serious flaws in previous results of the literature: we show a nonelementary memory lower bound for almost-sure winning whereas an exponential upper bound was previously claimed.", acknowledgement = ack-nhfb, articleno = "16", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Beckmann:2014:PGP, author = "Arnold Beckmann and Pavel Pudl{\'a}k and Neil Thapen", title = "Parity Games and Propositional Proofs", journal = j-TOCL, volume = "15", number = "2", pages = "17:1--17:??", month = apr, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2579822", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon May 5 17:57:30 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "A propositional proof system is weakly automatizable if there is a polynomial time algorithm that separates satisfiable formulas from formulas that have a short refutation in the system, with respect to a given length bound. We show that if the resolution proof system is weakly automatizable, then parity games can be decided in polynomial time. We give simple proofs that the same holds for depth-1 propositional calculus (where resolution has depth 0) with respect to mean payoff and simple stochastic games. We define a new type of combinatorial game and prove that resolution is weakly automatizable if and only if one can separate, by a set decidable in polynomial time, the games in which the first player has a positional winning strategy from the games in which the second player has a positional winning strategy. Our main technique is to show that a suitable weak bounded arithmetic theory proves that both players in a game cannot simultaneously have a winning strategy, and then to translate this proof into propositional form.", acknowledgement = ack-nhfb, articleno = "17", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Molinaro:2014:SSS, author = "Cristian Molinaro and Amy Sliva and V. S. Subrahmanian", title = "Super-Solutions: Succinctly Representing Solutions in Abductive Annotated Probabilistic Temporal Logic", journal = j-TOCL, volume = "15", number = "3", pages = "18:1--18:??", month = sep, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2627354", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Sep 8 19:06:46 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Annotated Probabilistic Temporal (APT) logic programs are a form of logic programs that allow users to state (or systems to automatically learn) rules of the form ``formula $G$ becomes true $ \Delta t$ time units after formula $F$ became true with $l$ to $u$ \% probability.'' In this article, we deal with abductive reasoning in APT logic: given an APT logic program $ \Pi $, a set of formulas $H$ that can be ``added'' to $ \Pi $, and a (temporal) goal $g$, is there a subset $S$ of $H$ such that $ \Pi \cup S$ is consistent and entails the goal $g$ ? In general, there are many different solutions to the problem and some of them can be highly repetitive, differing only in some unimportant temporal aspects. We propose a compact representation called super-solutions that succinctly represent sets of such solutions. Super-solutions are compact, but lossless representations of sets of such solutions. We study the complexity of existence of basic, super-, and maximal super-solutions as well as check if a set is a solution\slash super-solution\slash maximal super-solution. We then leverage a geometric characterization of the problem to suggest a set of pruning strategies and interesting properties that can be leveraged to make the search of basic and super-solutions more efficient. We propose correct sequential algorithms to find solutions and super-solutions. In addition, we develop parallel algorithms to find basic and super-solutions.", acknowledgement = ack-nhfb, articleno = "18", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Creignou:2014:CCL, author = "Nadia Creignou and Uwe Egly and Johannes Schmidt", title = "Complexity Classifications for Logic-Based Argumentation", journal = j-TOCL, volume = "15", number = "3", pages = "19:1--19:??", month = sep, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2629421", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Sep 8 19:06:46 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We consider logic-based argumentation in which an argument is a pair $ (\Phi, \alpha) $, where the support $ \Phi $ is a minimal consistent set of formulae taken from a given knowledge base (usually denoted by $ \Delta $) that entails the claim $ \alpha $ (a formula). We study the complexity of three central problems in argumentation: the existence of a support $ \Phi \subseteq \Delta $ , the verification of a support, and the relevance problem (given $ \psi $, is there a support $ \Phi $ such that $ \psi \in \Phi $ ?). When arguments are given in the full language of propositional logic, these problems are computationally costly tasks: the verification problem is DP-complete; the others are $ \Sigma^p_2$-complete. We study these problems in Schaefer's famous framework where the considered propositional formulae are in generalized conjunctive normal form. This means that formulae are conjunctions of constraints built upon a fixed finite set of Boolean relations $ \Gamma $ (the constraint language). We show that according to the properties of this language $ \Gamma $, deciding whether there exists a support for a claim in a given knowledge base is either polynomial, NP-complete, coNP-complete, or $ \Sigma^p_2$-complete. We present a dichotomous classification, P or DP-complete, for the verification problem and a trichotomous classification for the relevance problem into either polynomial, NP-complete, or $ \Sigma^p_2$-complete. These last two classifications are obtained by means of algebraic tools.", acknowledgement = ack-nhfb, articleno = "19", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Aschinger:2014:LLC, author = "Markus Aschinger and Conrad Drescher and Georg Gottlob and Heribert Vollmer", title = "{LoCo} --- a Logic for Configuration Problems", journal = j-TOCL, volume = "15", number = "3", pages = "20:1--20:??", month = sep, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2629454", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Sep 8 19:06:46 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In this work, we present LoCo, a fragment of classical first-order logic carefully tailored for expressing technical product configuration problems. The core feature of LoCo is that the number of components used in configurations does not have to be finitely bounded explicitly, but instead is bounded implicitly through the axioms. Computing configurations is equivalent to the task of model finding. We present the language, related algorithms, and complexity results as well as a prototypical implementation via answer set programming.", acknowledgement = ack-nhfb, articleno = "20", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Simmons:2014:SF, author = "Robert J. Simmons", title = "Structural Focalization", journal = j-TOCL, volume = "15", number = "3", pages = "21:1--21:??", month = sep, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2629678", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Sep 8 19:06:46 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Focusing, introduced by Jean-Marc Andreoli in the context of classical linear logic [Andreoli 1992], defines a normal form for sequent calculus derivations that cuts down on the number of possible derivations by eagerly applying invertible rules and grouping sequences of non-invertible rules. A focused sequent calculus is defined relative to some nonfocused sequent calculus; focalization is the property that every nonfocused derivation can be transformed into a focused derivation. In this article, we present a focused sequent calculus for propositional intuitionistic logic and prove the focalization property relative to a standard presentation of propositional intuitionistic logic. Compared to existing approaches, the proof is quite concise, depending only on the internal soundness and completeness of the focused logic. In turn, both of these properties can be established (and mechanically verified) by structural induction in the style of Pfenning's structural cut elimination without the need for any tedious and repetitious invertibility lemmas. The proof of cut admissibility for the focused system, which establishes internal soundness, is not particularly novel. The proof of identity expansion, which establishes internal completeness, is a major contribution of this work.", acknowledgement = ack-nhfb, articleno = "21", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Ying:2014:MCL, author = "Mingsheng Ying and Yangjia Li and Nengkun Yu and Yuan Feng", title = "Model-Checking Linear-Time Properties of Quantum Systems", journal = j-TOCL, volume = "15", number = "3", pages = "22:1--22:??", month = sep, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2629680", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Sep 8 19:06:46 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We define a formal framework for reasoning about linear-time properties of quantum systems in which quantum automata are employed in the modeling of systems and certain (closed) subspaces of state Hilbert spaces are used as the atomic propositions about the behavior of systems. We provide an algorithm for verifying invariants of quantum automata. Then, an automata-based model-checking technique is generalized for the verification of safety properties recognizable by reversible automata and $ \omega $-properties recognizable by reversible B{\"u}chi automata.", acknowledgement = ack-nhfb, articleno = "22", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Poza:2014:CRS, author = "Mar{\'\i}a Poza and C{\'e}sar Dom{\'\i}nguez and J{\'o}nathan Heras and Julio Rubio", title = "A Certified Reduction Strategy for Homological Image Processing", journal = j-TOCL, volume = "15", number = "3", pages = "23:1--23:??", month = sep, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2630789", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Sep 8 19:06:46 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The analysis of digital images using homological procedures is an outstanding topic in the area of Computational Algebraic Topology. In this article, we describe a certified reduction strategy to deal with digital images, but one preserving their homological properties. We stress both the advantages of our approach (mainly, the formalization of the mathematics allowing us to verify the correctness of algorithms) and some limitations (related to the performance of the running systems inside proof assistants). The drawbacks are overcome using techniques that provide an integration of computation and deduction. Our driving application is a problem in bioinformatics, where the accuracy and reliability of computations are specially requested.", acknowledgement = ack-nhfb, articleno = "23", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Carayol:2014:RAI, author = "Arnaud Carayol and Axel Haddad and Olivier Serre", title = "Randomization in Automata on Infinite Trees", journal = j-TOCL, volume = "15", number = "3", pages = "24:1--24:??", month = sep, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2629336", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Sep 8 19:06:46 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We study finite automata running over infinite binary trees. A run of such an automaton over an input tree is a tree labeled by control states of the automaton: the labeling is built in a top-down fashion and should be consistent with the transitions of the automaton. A branch in a run is accepting if the $ \omega $-word obtained by reading the states along the branch satisfies some acceptance condition (typically an $ \omega $-regular condition such as a B{\"u}chi or a parity condition). Finally, a tree is accepted by the automaton if there exists a run over this tree in which every branch is accepting. In this article, we consider two relaxations of this definition, introducing a qualitative aspect. First, we relax the notion of accepting run by allowing a negligible set (in the sense of measure theory) of nonaccepting branches. In this qualitative setting, a tree is accepted by the automaton if there exists a run over this tree in which almost every branch is accepting. This leads to a new class of tree languages, qualitative tree languages. This class enjoys many good properties: closure under union and intersection (but not under complement), and emptiness is decidable in polynomial time. A dual class, positive tree languages, is defined by requiring that an accepting run contains a non-negligeable set of branches. The second relaxation is to replace the existential quantification (a tree is accepted if there exists some accepting run over the input tree) with a probabilistic quantification (a tree is accepted if almost every run over the input tree is accepting). For the run, we may use either classical acceptance or qualitative acceptance. In particular, for the latter, we exhibit a tight connection with partial observation Markov decision processes. Moreover, if we additionally restrict operation to the B{\"u}chi condition, we show that it leads to a class of probabilistic automata on infinite trees enjoying a decidable emptiness problem. To our knowledge, this is the first positive result for a class of probabilistic automaton over infinite trees.", acknowledgement = ack-nhfb, articleno = "24", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Artale:2014:CTC, author = "Alessandro Artale and Roman Kontchakov and Vladislav Ryzhikov and Michael Zakharyaschev", title = "A Cookbook for Temporal Conceptual Data Modelling with Description Logics", journal = j-TOCL, volume = "15", number = "3", pages = "25:1--25:??", month = sep, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2629565", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Sep 8 19:06:46 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We design temporal description logics (TDLs) suitable for reasoning about temporal conceptual data models and investigate their computational complexity. Our formalisms are based on DL-Lite logics with three types of concept inclusions (ranging from atomic concept inclusions and disjointness to the full Booleans), as well as cardinality constraints and role inclusions. The logics are interpreted over the Cartesian products of object domains and the flow of time (Z, {$<$}), satisfying the constant domain assumption. Concept and role inclusions of the TBox hold at all moments of time (globally), and data assertions of the ABox hold at specified moments of time. To express temporal constraints of conceptual data models, the languages are equipped with flexible and rigid roles, standard future and past temporal operators on concepts, and operators ``always'' and ``sometime'' on roles. The most expressive of our TDLs (which can capture lifespan cardinalities and either qualitative or quantitative evolution constraints) turns out to be undecidable. However, by omitting some of the temporal operators on concepts/roles or by restricting the form of concept inclusions, we construct logics whose complexity ranges between NL ogSpace and PSpace. These positive results are obtained by reduction to various clausal fragments of propositional temporal logic, which opens a way to employ propositional or first-order temporal provers for reasoning about temporal data models.", acknowledgement = ack-nhfb, articleno = "25", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Goller:2014:RPR, author = "Stefan G{\"o}ller and Anthony Widjaja Lin", title = "Refining the Process Rewrite Systems Hierarchy via Ground Tree Rewrite Systems", journal = j-TOCL, volume = "15", number = "4", pages = "26:1--26:??", month = sep, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2629679", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Sep 13 07:31:07 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In his seminal paper, Mayr introduced the well-known process rewrite systems (PRS) hierarchy, which contains many well-studied classes of infinite-state systems including pushdown systems (PDS), Petri nets, and PA-processes. A separate development in the term rewriting community introduced the notion of ground tree rewrite systems (GTRS), which is a model that strictly extends PDS while still enjoying desirable decidable properties. There have been striking similarities between the verification problems that have been shown decidable (and undecidable) over GTRS and over models in the PRS hierarchy such as PA and PAD processes. It is open to what extent PRS and GTRS are connected in terms of their expressive power. In this article, we pinpoint the exact connection between GTRS and models in the PRS hierarchy in terms of their expressive power with respect to strong, weak, and branching bisimulation. Among others, this connection allows us to give new insights into the decidability results for subclasses of PRS, such as simpler proofs of known decidability results of verifications problems on PAD.", acknowledgement = ack-nhfb, articleno = "26", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Boker:2014:TSA, author = "Udi Boker and Krishnendu Chatterjee and Thomas A. Henzinger and Orna Kupferman", title = "Temporal Specifications with Accumulative Values", journal = j-TOCL, volume = "15", number = "4", pages = "27:1--27:??", month = sep, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2629686", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Sep 13 07:31:07 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Recently, there has been an effort to add quantitative objectives to formal verification and synthesis. We introduce and investigate the extension of temporal logics with quantitative atomic assertions. At the heart of quantitative objectives lies the accumulation of values along a computation. It is often the accumulated sum, as with energy objectives, or the accumulated average, as with mean-payoff objectives. We investigate the extension of temporal logics with the prefix-accumulation assertions Sum( v ) {$>$}= c and Avg( v ) {$>$}= c, where v is a numeric (or Boolean) variable of the system, c is a constant rational number, and Sum( v ) and Avg( v ) denote the accumulated sum and average of the values of v from the beginning of the computation up to the current point in time. We also allow the path-accumulation assertions LimInfAvg( v ){$>$}= c and LimSupAvg( v ){$>$}= c, referring to the average value along an entire infinite computation. We study the border of decidability for such quantitative extensions of various temporal logics. In particular, we show that extending the fragment of CTL that has only the EX, EF, AX, and AG temporal modalities with both prefix-accumulation assertions, or extending LTL with both path-accumulation assertions, results in temporal logics whose model-checking problem is decidable. Moreover, the prefix-accumulation assertions may be generalized with ``controlled accumulation,'' allowing, for example, to specify constraints on the average waiting time between a request and a grant. On the negative side, we show that this branching-time logic is, in a sense, the maximal logic with one or both of the prefix-accumulation assertions that permits a decidable model-checking procedure. Extending a temporal logic that has the EG or EU modalities, such as CTL or LTL, makes the problem undecidable.", acknowledgement = ack-nhfb, articleno = "27", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Komosinski:2014:IEA, author = "Maciej Komosinski and Adam Kups and Dorota Leszczy{\'n}ska-Jasion and Mariusz Urba{\'n}ski", title = "Identifying Efficient Abductive Hypotheses Using Multicriteria Dominance Relation", journal = j-TOCL, volume = "15", number = "4", pages = "28:1--28:??", month = sep, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2629669", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Sep 13 07:31:07 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In this article, results of the automation of an abductive procedure are reported. This work is a continuation of our earlier research [Komosinski et al. 2012], where a general scheme of the procedure has been proposed. Here, a more advanced system developed to generate and evaluate abductive hypotheses is introduced. Abductive hypotheses have been generated by the implementation of the synthetic tableau method. Prior to the evaluation, the set of hypotheses has undergone several reduction phases. To assess usefulness of abductive hypotheses in the reduced set, several criteria have been employed. The evaluation of efficiency of the hypotheses has been provided by the multicriteria dominance relation. To comprehend the abductive procedure and the evaluation process more extensively, analyses have been conducted on a number of artificially generated abductive problems.", acknowledgement = ack-nhfb, articleno = "28", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Frigeri:2014:FTL, author = "Achille Frigeri and Liliana Pasquale and Paola Spoletini", title = "Fuzzy Time in Linear Temporal Logic", journal = j-TOCL, volume = "15", number = "4", pages = "30:1--30:??", month = sep, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2629606", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Sep 13 07:31:07 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In the past years, the adoption of adaptive systems has increased in many fields of computer science, such as databases and software engineering. These systems are able to automatically react to events by collecting information from the external environment and generating new events. However, the collection of data is often hampered by uncertainty and vagueness. The decision-making mechanism used to produce a reaction is also imprecise and cannot be evaluated in a crisp way, as it depends on vague temporal constraints expressed by humans. Logic has been extensively used as an abstraction to express vagueness in the satisfaction of system properties, as well as to enrich existing modeling formalisms. However, existing attempts to fuzzify the temporal modalities still have some limitations. Existing fuzzy temporal languages are generally obtained from classical temporal logic by replacing classical connectives or propositions with their fuzzy counterparts. Hence, these languages do not allow us to represent temporal properties, such as ``almost always'' and ``soon,'' in which the notion of time is inherently fuzzy. To overcome these limitations, we propose a temporal framework, fuzzy-time temporal logic (FTL), to express vagueness on time. This framework formally defines a set of fuzzy temporal modalities that can be customized by choosing a specific semantics for the connectives. The semantics of the language is sound, and the introduced modalities respect a set of mutual relations. We also prove that under the assumption that all events are crisp, FTL reduces to linear temporal logic (LTL). Moreover, for some of the possible fuzzy interpretations of the connectives, we identify adequate sets of temporal operators, from which it is possible to derive all of the other ones.", acknowledgement = ack-nhfb, articleno = "30", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Schellhorn:2014:SCP, author = "Gerhard Schellhorn and John Derrick and Heike Wehrheim", title = "A Sound and Complete Proof Technique for Linearizability of Concurrent Data Structures", journal = j-TOCL, volume = "15", number = "4", pages = "31:1--31:??", month = sep, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2629496", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Sep 13 07:31:07 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Efficient implementations of data structures such as queues, stacks or hash-tables allow for concurrent access by many processes at the same time. To increase concurrency, these algorithms often completely dispose with locking, or only lock small parts of the structure. Linearizability is the standard correctness criterion for such a scenario-where a concurrent object is linearizable if all of its operations appear to take effect instantaneously some time between their invocation and return. The potential concurrent access to the shared data structure tremendously increases the complexity of the verification problem, and thus current proof techniques for showing linearizability are all tailored to specific types of data structures. In previous work, we have shown how simulation-based proof conditions for linearizability can be used to verify a number of subtle concurrent algorithms. In this article, we now show that conditions based on backward simulation can be used to show linearizability of every linearizable algorithm, that is, we show that our proof technique is both sound and complete. We exemplify our approach by a linearizability proof of a concurrent queue, introduced in Herlihy and Wing's landmark paper on linearizability. Except for their manual proof, none of the numerous other approaches have successfully treated this queue. Our approach is supported by a full mechanisation: both the linearizability proofs for case studies like the queue, and the proofs of soundness and completeness have been carried out with an interactive prover, which is KIV.", acknowledgement = ack-nhfb, articleno = "31", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Riguzzi:2014:TEL, author = "Fabrizio Riguzzi and Terrance Swift", title = "Terminating Evaluation of Logic Programs with Finite Three-Valued Models", journal = j-TOCL, volume = "15", number = "4", pages = "32:1--32:??", month = sep, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2629337", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Sep 13 07:31:07 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "As evaluation methods for logic programs have become more sophisticated, the classes of programs for which termination can be guaranteed have expanded. From the perspective of ar set programs that include function symbols, recent work has identified classes for which grounding routines can terminate either on the entire program [Calimeri et al. 2008] or on suitable queries [Baselice et al. 2009]. From the perspective of tabling, it has long been known that a tabling technique called subgoal abstraction provides good termination properties for definite programs [Tamaki and Sato 1986], and this result was recently extended to stratified programs via the class of bounded term-size programs [Riguzzi and Swift 2013]. In this article, we provide a formal definition of tabling with subgoal abstraction resulting in the SLG$_{SA}$ algorithm. Moreover, we discuss a declarative characterization of the queries and programs for which SLG$_{SA}$ terminates. We call this class strongly bounded term-size programs and show its equivalence to programs with finite well-founded models. For normal programs, strongly bounded term-size programs strictly includes the finitely ground programs of Calimeri et al. [2008]. SLG$_{SA}$ has an asymptotic complexity on strongly bounded term-size programs equal to the best known and produces a residual program that can be sent to an answer set programming system. Finally, we describe the implementation of subgoal abstraction within the SLG-WAM of XSB and provide performance results.", acknowledgement = ack-nhfb, articleno = "32", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Zanardini:2014:IFS, author = "Damiano Zanardini and Samir Genaim", title = "Inference of Field-Sensitive Reachability and Cyclicity", journal = j-TOCL, volume = "15", number = "4", pages = "33:1--33:??", month = sep, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2629478", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Sep 13 07:31:07 MDT 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In heap-based languages, knowing that a variable x points to an acyclic data structure is useful for analyzing termination. This information guarantees that the depth of the data structure to which x points is greater than the depth of the structure pointed to by x. fld, and allows bounding the number of iterations of a loop that traverses the data structure on fld. In general, proving termination needs acyclicity, unless program-specific or nonautomated reasoning is performed. However, recent work could prove that certain loops terminate even without inferring acyclicity, because they traverse data structures ``acyclically.'' Consider a double-linked list: if it is possible to demonstrate that every cycle involves both the ``next'' and the ``prev'' field, then a traversal on ``next'' terminates since no cycle will be traversed completely. This article develops a static analysis inferring field-sensitive reachability and cyclicity information, which is more general than existing approaches. Propositional formul{\ae} are computed, which describe which fields may or may not be traversed by paths in the heap. Consider a tree with edges ``left'' and ``right'' to the left and right subtrees, and ``parent'' to the parent node: termination of a loop traversing leaf-up cannot be guaranteed by state-of-the-art analyses. Instead, propositional formul{\ae} computed by this analysis indicate that cycles must traverse ``parent'' and at least one between ``left'' and ``right'': termination is guaranteed, as no cycle is traversed completely. This work defines the necessary abstract domains and builds an abstract semantics on them. A prototypical implementation provides the expected result on relevant examples.", acknowledgement = ack-nhfb, articleno = "33", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Mogavero:2014:RAS, author = "Fabio Mogavero and Aniello Murano and Giuseppe Perelli and Moshe Y. Vardi", title = "Reasoning About Strategies: On the Model-Checking Problem", journal = j-TOCL, volume = "15", number = "4", pages = "34:1--34:??", month = nov, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2631917", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Nov 24 15:22:24 MST 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In open systems verification, to formally check for reliability, one needs an appropriate formalism to model the interaction between agents and express the correctness of the system no matter how the environment behaves. An important contribution in this context is given by modal logics for strategic ability, in the setting of multiagent games, such as Atl, Atl*, and the like. Recently, Chatterjee, Henzinger, and Piterman introduced Strategy Logic, which we denote here by CHP-Sl, with the aim of getting a powerful framework for reasoning explicitly about strategies. CHP-Sl is obtained by using first-order quantifications over strategies and has been investigated in the very specific setting of two-agents turned-based games, where a nonelementary model-checking algorithm has been provided. While CHP-Sl is a very expressive logic, we claim that it does not fully capture the strategic aspects of multiagent systems. In this article, we introduce and study a more general strategy logic, denoted Sl, for reasoning about strategies in multiagent concurrent games. As a key aspect, strategies in Sl are not intrinsically glued to a specific agent, but an explicit binding operator allows an agent to bind to a strategy variable. This allows agents to share strategies or reuse one previously adopted. We prove that Sl strictly includes CHP-Sl, while maintaining a decidable model-checking problem. In particular, the algorithm we propose is computationally not harder than the best one known for CHP-Sl. Moreover, we prove that such a problem for Sl is NonElementary. This negative result has spurred us to investigate syntactic fragments of Sl, strictly subsuming Atl*, with the hope of obtaining an elementary model-checking problem. Among others, we introduce and study the sublogics Sl[ng], Sl[bg], and Sl[1g]. They encompass formulas in a special prenex normal form having, respectively, nested temporal goals, Boolean combinations of goals, and, a single goal at a time. Intuitively, for a goal, we mean a sequence of bindings, one for each agent, followed by an Ltl formula. We prove that the model-checking problem for Sl[1g] is 2ExpTime-complete, thus not harder than the one for Atl*. In contrast, Sl[ng] turns out to be NonElementary-hard, strengthening the corresponding result for Sl. Regarding Sl[bg], we show that it includes CHP-Sl and its model-checking is decidable with a 2ExpTimelower-bound. It is worth enlightening that to achieve the positive results about S l[1g], we introduce a fundamental property of the semantics of this logic, called behavioral, which allows to strongly simplify the reasoning about strategies. Indeed, in a nonbehavioral logic such as Sl[bg] and the subsuming ones, to satisfy a formula, one has to take into account that a move of an agent, at a given moment of a play, may depend on the moves taken by any agent in another counterfactual play.", acknowledgement = ack-nhfb, articleno = "34", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bonchi:2014:GTB, author = "Filippo Bonchi and Fabio Gadducci and Giacoma Valentina Monreale", title = "A General Theory of Barbs, Contexts, and Labels", journal = j-TOCL, volume = "15", number = "4", pages = "35:1--35:??", month = nov, year = "2014", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2631916", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Nov 24 15:22:24 MST 2014", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Barbed bisimilarity is a widely used behavioral equivalence for interactive systems: given a set of predicates (denoted ``barbs'' and representing basic observations on states) and a set of contexts (representing the possible execution environments), two systems are deemed to be equivalent if they verify the same barbs whenever inserted inside any of the chosen contexts. Despite its flexibility and expressiveness, this definition of equivalence is unsatisfactory because often the quantification is over an infinite set of contexts, thus making barbed bisimilarity very hard to be verified. Should a labeled operational semantics be available, more efficient observational equivalences might be adopted. To this end, a series of techniques has been proposed to derive labeled transition systems (LTSs) from unlabeled ones, the main example being Leifer and Milner's theory of reactive systems. The underlying intuition is that labels should be the ``minimal'' contexts that allow for a reduction step to be performed. However, minimality is difficult to asses, whereas the set of ``intuitively'' correct labels is often easily devised by the ingenuity of the researcher. This article introduces a framework that characterizes (weak) barbed bisimilarity via LTSs whose labels are (not necessarily minimal) contexts. Differently from previous proposals, our theory does not depend on the way the labeled transitions are built but instead relies on a simple set-theoretical presentation for identifying those properties such an LTS should verify to (1) capture the barbed bisimilarities of the underlying system and (2) ensure that such bisimilarities are congruences. Furthermore, we adopt suitable proof techniques to make feasible the verification of such properties. To provide a test-bed for our formalism, we instantiate it by addressing the semantics of the Mobile Ambients calculus, recasting its barbed bisimilarities via label-based behavioral equivalences.", acknowledgement = ack-nhfb, articleno = "35", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Halamish:2015:MDL, author = "Shulamit Halamish and Orna Kupferman", title = "Minimizing Deterministic Lattice Automata", journal = j-TOCL, volume = "16", number = "1", pages = "1:1--1:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2631915", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Mar 24 17:04:26 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Traditional automata accept or reject their input and are therefore Boolean. In contrast, weighted automata map each word to a value from a semiring over a large domain. The special case of lattice automata, in which the semiring is a finite lattice, has interesting theoretical properties as well as applications in formal methods. A minimal deterministic automaton captures the combinatorial nature and complexity of a formal language. Deterministic automata are used in runtime monitoring, pattern recognition, and modeling systems. Thus, the minimization problem for deterministic automata is of great interest, both theoretically and in practice. For deterministic traditional automata on finite words, a minimization algorithm, based on the Myhill--Nerode right congruence on the set of words, generates in polynomial time a canonical minimal deterministic automaton. A polynomial algorithm is known also for deterministic weighted automata over the tropical semiring. For general deterministic weighted automata, the problem of minimization is open. In this article, we study minimization of deterministic lattice automata. We show that it is impossible to define a right congruence in the context of lattices, and that no canonical minimal automaton exists. Consequently, the minimization problem is much more complicated, and we prove that it is NP-complete. As good news, we show that while right congruence fails already for finite lattices that are fully ordered, for this setting we are able to combine a finite number of right congruences and generate a minimal deterministic automaton in polynomial time.", acknowledgement = ack-nhfb, articleno = "1", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Crafa:2015:LCB, author = "Silvia Crafa and Francesco Ranzato", title = "Logical Characterizations of Behavioral Relations on Transition Systems of Probability Distributions", journal = j-TOCL, volume = "16", number = "1", pages = "2:1--2:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2641566", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Mar 6 10:01:34 MST 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Probabilistic nondeterministic processes are commonly modeled as probabilistic LTSs (PLTSs). A number of logical characterizations of the main behavioral relations on PLTSs have been studied. In particular, Parma and Segala [2007] and Hermanns et al. [2011] define a probabilistic Hennessy--Milner logic interpreted over probability distributions, whose corresponding logical equivalence/preorder when restricted to Dirac distributions coincides with standard bisimulation/simulation between the states of a PLTS. This result is here extended by studying the full logical equivalence/preorder between (possibly non-Dirac) distributions in terms of a notion of bisimulation/simulation defined on an LTS whose states are distributions (dLTS). We show that the well-known spectrum of behavioral relations on nonprobabilistic LTSs as well as their corresponding logical characterizations in terms of Hennessy--Milner logic scales to the probabilistic setting when considering dLTSs.", acknowledgement = ack-nhfb, articleno = "2", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Tao:2015:CFS, author = "Jia Tao and Giora Slutzki and Vasant Honavar", title = "A Conceptual Framework for Secrecy-preserving Reasoning in Knowledge Bases", journal = j-TOCL, volume = "16", number = "1", pages = "3:1--3:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2637477", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Mar 6 10:01:34 MST 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In many applications, Knowledge Bases (KBs) contain confidential or private information (secrets). The KB should be able to use this secret information in its reasoning process but in answering user queries care must be exercised so that secrets are not revealed to unauthorized users. We consider this problem under the Open World Assumption (OWA) in a setting with multiple querying agents $ M_1 $, \ldots{}, $ M_m $ that can pose queries against the KB K and selectively share answers that they receive from K with one or more other querying agents. We assume that for each $ M_i $, the KB has a prespecified set of secrets $ S_i $ that need to be protected from $ M_i $. Communication between querying agents is modeled by a communication graph, a directed graph with self-loops. We introduce a general framework and propose an approach to secrecy-preserving query answering based on sound and complete proof systems. The idea is to hide the truthful answer from a querying agent $ M_i $ by feigning ignorance without lying (i.e., to provide the answer `Unknown' to a query $q$ if it needs to be protected). Under the OWA, a querying agent cannot distinguish between the case that $q$ is being protected (for reasons of secrecy) and the case that it cannot be inferred from K. In the pre-query stage we compute a set of envelopes $ E_1$, \ldots{}, $ E_m$ (restricted to a finite subset of the set of formulae that are entailed by K) so that $ S_i \subseteq E_i$, and a query \alpha posed by agent $ M_i$ can be answered truthfully whenever $ \alpha \not \in E_i$ and $ \isonot \alpha \not \in E_i$. After the pre-query stage, the envelope is updated as needed. We illustrate this approach with two simple cases: the Propositional Horn KBs and the Description Logic AL KBs.", acknowledgement = ack-nhfb, articleno = "3", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Biscaia:2015:DAS, author = "M. Biscaia and D. Henriques and P. Mateus", title = "Decidability of Approximate {Skolem} Problem and Applications to Logical Verification of Dynamical Properties of {Markov} Chains", journal = j-TOCL, volume = "16", number = "1", pages = "4:1--4:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2666772", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Mar 6 10:01:34 MST 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "When studying probabilistic dynamical systems, temporal logic has typically been used to analyze path properties. Recently, there has been some interest in analyzing the dynamical evolution of state probabilities of these systems. In this article, we show that verifying linear temporal properties concerning the state evolution induced by a Markov chain is equivalent to the decidability of the Skolem problem --- a long-standing open problem in Number Theory. However, from a practical point of view, usually it is enough to check properties up to some acceptable error bound $ \epsilon $. We show that an approximate version of the Skolem problem is decidable, and that it can be applied to verify, up to arbitrarily small $ \epsilon $, linear temporal properties of the state evolution induced by a Markov chain.", acknowledgement = ack-nhfb, articleno = "4", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Ciabattoni:2015:TPO, author = "Agata Ciabattoni and Ori Lahav and Lara Spendier and Anna Zamansky", title = "Taming Paraconsistent (and Other) Logics: an Algorithmic Approach", journal = j-TOCL, volume = "16", number = "1", pages = "5:1--5:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2661636", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Mar 6 10:01:34 MST 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We develop a fully algorithmic approach to ``taming'' logics expressed Hilbert style, that is, reformulating them in terms of analytic sequent calculi and useful semantics. Our approach applies to Hilbert calculi extending the positive fragment of propositional classical logic with axioms of a certain general form that contain new unary connectives. Our work encompasses various results already obtained for specific logics. It can be applied to new logics, as well as to known logics for which an analytic calculus or a useful semantics has so far not been available. A Prolog implementation of the method is described.", acknowledgement = ack-nhfb, articleno = "5", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Avni:2015:PWC, author = "Guy Avni and Orna Kupferman", title = "Parameterized Weighted Containment", journal = j-TOCL, volume = "16", number = "1", pages = "6:1--6:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2665076", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Mar 6 10:01:34 MST 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Partially specified systems and specifications are used in formal methods such as stepwise design and query checking. Existing methods consider a setting in which systems and their correctness are Boolean. In recent years, there has been growing interest and need for quantitative formal methods, where systems may be weighted and specifications may be multivalued. Weighted automata, which map input words to a numerical value, play a key role in quantitative reasoning. Technically, every transition in a weighted automaton A has a cost, and the value A assigns to a finite word w is the sum of the costs on the transitions traversed along the most expensive accepting run of A on w. We study parameterized weighted containment: given three weighted automata A, B, and C, with B being partial, the goal is to find an assignment to the missing costs in B so that we end up with B ' for which B '{$<$}= C, where {$<$}= is the weighted counterpart of containment. We also consider a one-sided version of the problem, where only A or only C is given in addition to B, and the goal is to find a minimal assignment with which A {$<$}= B ' or, respectively, a maximal one with which B ' {$<$}= C. We argue that both problems are useful in stepwise design of weighted systems as well as approximated minimization of weighted automata. We show that when the automata are deterministic, we can solve the problems in polynomial time. Our solution is based on the observation that the set of legal assignments to k missing costs forms a k -dimensional polytope. The technical challenge is to find an assignment in polynomial time even though the polytope is defined by means of exponentially many inequalities. We do so by developing a divide-and-conquer algorithm based on a separation oracle for polytopes. For nondeterministic automata, the weighted setting is much more complex, and in fact even nonparameterized containment is undecidable. We are able to show positive results for variants of the problems, where containment is replaced by simulation.", acknowledgement = ack-nhfb, articleno = "6", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Fontaine:2015:WIH, author = "Ga{\"e}lle Fontaine", title = "Why Is It Hard to Obtain a Dichotomy for Consistent Query Answering?", journal = j-TOCL, volume = "16", number = "1", pages = "7:1--7:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2699912", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Mar 24 17:04:26 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "A database may for various reasons become inconsistent with respect to a given set of integrity constraints. In the late 1990s, the formal approach of consistent query answering was proposed in order to query such databases. Since then, a lot of efforts have been spent to classify the complexity of consistent query answering under various classes of constraints. It is known that for the most common constraints and queries, the problem is in coNP and might be coNP-hard, yet several relevant tractable classes have been identified. Additionally, the results that emerged suggested that given a set of key constraints and a conjunctive query, the problem of consistent query answering is either in PTime or is coNP-complete. However, despite all the work, as of today this dichotomy remains a conjecture. The main contribution of this article is to explain why it appears so difficult to obtain a dichotomy result in the setting of consistent query answering. Namely, we prove that such a dichotomy with respect to common classes of constraints and queries is harder to achieve than a dichotomy for the constraint satisfaction problem, which is a famous open problem since the 1990s.", acknowledgement = ack-nhfb, articleno = "7", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Ferrari:2015:EDD, author = "Mauro Ferrari and Camillo Fiorentini and Guido Fiorino", title = "An Evaluation-Driven Decision Procedure for {G3i}", journal = j-TOCL, volume = "16", number = "1", pages = "8:1--8:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2660770", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Mar 24 17:04:26 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "It is well known that G3i, the sequent calculus for intuitionistic propositional logic where weakening and contraction are absorbed into the rules, is not terminating. Indeed, due to the contraction in the rule for left implication, the na{\"\i}ve goal-oriented proof-search strategy, consisting in applying the rules of the calculus bottom up until possible, can generate branches of infinite length. The usual solution to this problem is to support the proof-search procedure with a loop checking mechanism that prevents the generation of infinite branches by storing and analyzing some information regarding the branch under development. In this article, we propose a new technique based on evaluation functions. An evaluation function is a lightweight computational mechanism that, analyzing only the current goal of the proof search, allows one to drive the application of rules to guarantee termination and to avoid useless backtracking. We describe an evaluation-driven proof-search procedure that given a sequent $\sigma$ returns either a G3i-derivation of $\sigma$ or a countermodel for $\sigma$. We prove that such a procedure is terminating and correct, and that the depth of the G3i-trees generated during proof search is quadratic in the size of $\sigma$. Finally, we discuss the overhead time introduced by evaluation functions in the proof-search procedure.", acknowledgement = ack-nhfb, articleno = "8", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Goller:2015:CDM, author = "Stefan G{\"o}ller and Jean-Christoph Jung and Markus Lohrey", title = "The Complexity of Decomposing Modal and First-Order Theories", journal = j-TOCL, volume = "16", number = "1", pages = "9:1--9:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2699918", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Tue Mar 24 17:04:26 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We study the satisfiability problem of the logic $ K^2 = K \times K $ --- the two-dimensional variant of unimodal logic, where models are restricted to asynchronous products of two Kripke frames. Gabbay and Shehtman proved in 1998 that this problem is decidable in a tower of exponentials. So far, the best-known lower bound is NEXP-hardness shown by Marx and Mikul{\'a}s in 2001. Our first main result closes this complexity gap. We show that satisfiability in $ K^2 $ is nonelementary. More precisely, we prove that it is $k$-NEXP-complete, where $k$ is the switching depth (the minimal modal rank among the two dimensions) of the input formula, hereby solving a conjecture of Marx and Mikul{\'a}s. Using our lower-bound technique also allows us to derive nonelementary lower bounds for the two-dimensional modal logics $ K4 \times K$ and $ S5_2 \times K$, for which only elementary lower bounds were previously known. Moreover, we apply our technique to prove nonelementary lower bounds for the sizes of Feferman-Vaught decompositions with respect to product for any decomposable logic that is at least as expressive as unimodal $K$, generalizing a recent result by the first author and Lin. For the three-variable fragment FO$^3$ of first-order logic, we obtain the following two immediate corollaries: the size of Feferman-Vaught decompositions with respect to disjoint sum are inherently nonelementary, and equivalent formulas in Gaifman normal form are inherently nonelementary. Our second main result consists in providing effective elementary (more precisely, doubly exponential) upper bounds for the two-variable fragment FO$^2$ of first-order logic both for Feferman-Vaught decompositions and for equivalent formulas in Gaifman normal form.", acknowledgement = ack-nhfb, articleno = "9", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Simonsen:2015:CRS, author = "Jakob Grue Simonsen", title = "A Confluent Rewriting System Having No Computable, One-Step, Normalizing Strategy", journal = j-TOCL, volume = "16", number = "2", pages = "10:1--10:??", month = feb, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2699917", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Mar 6 10:01:37 MST 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "A full and finitely generated Church--Rosser term rewriting system is presented that has no computable one-step, normalizing strategy; the system is both left- and right-linear. The result provides a negative answer to a question posed by Kennaway in 1989: Number 10 on the List of Open Problems in Rewriting.", acknowledgement = ack-nhfb, articleno = "10", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Skarlatidis:2015:PEC, author = "Anastasios Skarlatidis and Georgios Paliouras and Alexander Artikis and George A. Vouros", title = "Probabilistic Event Calculus for Event Recognition", journal = j-TOCL, volume = "16", number = "2", pages = "11:1--11:??", month = feb, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2699916", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Mar 6 10:01:37 MST 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Symbolic event recognition systems have been successfully applied to a variety of application domains, extracting useful information in the form of events, allowing experts or other systems to monitor and respond when significant events are recognised. In a typical event recognition application, however, these systems often have to deal with a significant amount of uncertainty. In this article, we address the issue of uncertainty in logic-based event recognition by extending the Event Calculus with probabilistic reasoning. Markov logic networks are a natural candidate for our logic-based formalism. However, the temporal semantics of the Event Calculus introduce a number of challenges for the proposed model. We show how and under what assumptions we can overcome these problems. Additionally, we study how probabilistic modelling changes the behaviour of the formalism, affecting its key property-the inertia of fluents. Furthermore, we demonstrate the advantages of the probabilistic Event Calculus through examples and experiments in the domain of activity recognition, using a publicly available dataset for video surveillance.", acknowledgement = ack-nhfb, articleno = "11", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Sebastiani:2015:OMT, author = "Roberto Sebastiani and Silvia Tomasi", title = "Optimization Modulo Theories with Linear Rational Costs", journal = j-TOCL, volume = "16", number = "2", pages = "12:1--12:??", month = feb, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2699915", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Mar 6 10:01:37 MST 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In the contexts of automated reasoning (AR) and formal verification (FV), important decision problems are effectively encoded into Satisfiability Modulo Theories (SMT). In the last decade, efficient SMT solvers have been developed for several theories of practical interest (e.g., linear arithmetic, arrays, and bit vectors). Surprisingly, little work has been done to extend SMT to deal with optimization problems; in particular, we are not aware of any previous work on SMT solvers able to produce solutions that minimize cost functions over arithmetical variables. This is unfortunate, since some problems of interest require this functionality. In the work described in this article we start filling this gap. We present and discuss two general procedures for leveraging SMT to handle the minimization of linear rational cost functions, combining SMT with standard minimization techniques. We have implemented the procedures within the MathSAT SMT solver. Due to the absence of competitors in the AR, FV, and SMT domains, we have experimentally evaluated our implementation against state-of-the-art tools for the domain of Linear Generalized Disjunctive Programming (LGDP), which is closest in spirit to our domain, on sets of problems that have been previously proposed as benchmarks for the latter tools. The results show that our tool is very competitive with, and often outperforms, these tools on these problems, clearly demonstrating the potential of the approach.", acknowledgement = ack-nhfb, articleno = "12", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Jouannaud:2015:NHO, author = "Jean-Pierre Jouannaud and Albert Rubio", title = "Normal Higher-Order Termination", journal = j-TOCL, volume = "16", number = "2", pages = "13:1--13:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2699913", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 7 09:04:46 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We extend the termination proof methods based on reduction orderings to higher-order rewriting systems based on higher-order pattern matching. We accommodate, on the one hand, a weakly polymorphic, algebraic extension of Church's simply typed $ \lambda $-calculus and, on the other hand, any use of eta, as a reduction, as an expansion, or as an equation. The user's rules may be of any type in this type system, either a base, functional, or weakly polymorphic type.", acknowledgement = ack-nhfb, articleno = "13", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Felgenhauer:2015:LSP, author = "Bertram Felgenhauer and Aart Middeldorp and Harald Zankl and Vincent {Van Oostrom}", title = "Layer Systems for Proving Confluence", journal = j-TOCL, volume = "16", number = "2", pages = "14:1--14:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2710017", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 7 09:04:46 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We introduce layer systems for proving generalizations of the modularity of confluence for first-order rewrite systems. Layer systems specify how terms can be divided into layers. We establish structural conditions on those systems that imply confluence. Our abstract framework covers known results like modularity, many-sorted persistence, layer-preservation, and currying. We present a counterexample to an extension of persistence to order-sorted rewriting and derive new sufficient conditions for the extension to hold. All our proofs are constructive.", acknowledgement = ack-nhfb, articleno = "14", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Demri:2015:TVS, author = "St{\'e}phane Demri and Morgan Deters", title = "Two-Variable Separation Logic and Its Inner Circle", journal = j-TOCL, volume = "16", number = "2", pages = "15:1--15:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2724711", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 7 09:04:46 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Separation logic is a well-known assertion language for Hoare-style proof systems. We show that first-order separation logic with a unique record field restricted to two quantified variables and no program variables is undecidable. This is among the smallest fragments of separation logic known to be undecidable, and this contrasts with the decidability of two-variable first-order logic. We also investigate its restriction by dropping the magic wand connective, known to be decidable with nonelementary complexity, and we show that the satisfiability problem with only two quantified variables is not yet elementary recursive. Furthermore, we establish insightful and concrete relationships between two-variable separation logic and propositional interval temporal logic (PITL), data logics, and modal logics, providing an inner circle of closely related logics.", acknowledgement = ack-nhfb, articleno = "15", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Geneves:2015:EDC, author = "Pierre Genev{\`e}s and Nabil Laya{\"\i}da and Alan Schmitt and Nils Gesbert", title = "Efficiently Deciding $ \mu $-Calculus with Converse over Finite Trees", journal = j-TOCL, volume = "16", number = "2", pages = "16:1--16:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2724712", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 7 09:04:46 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We present a sound and complete satisfiability-testing algorithm and its effective implementation for an alternation-free modal $ \mu $-calculus with converse, where formulas are cycle-free and are interpreted over finite ordered trees. The time complexity of the satisfiability-testing algorithm is $ 2^{O(n)}$ in terms of formula size n. The algorithm is implemented using symbolic techniques (BDD). We present crucial implementation techniques and heuristics that we used to make the algorithm as fast as possible in practice. Our implementation is available online and can be used to solve logical formulas of significant size and practical value. We illustrate this in the setting of XML trees.", acknowledgement = ack-nhfb, articleno = "16", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Kopczynski:2015:VHF, author = "Eryk Kopczy{\'n}ski and Tony Tan", title = "On the Variable Hierarchy of First-Order Spectra", journal = j-TOCL, volume = "16", number = "2", pages = "17:1--17:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2733376", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 7 09:04:46 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The spectrum of a first-order logic sentence is the set of natural numbers that are cardinalities of its finite models. In this article, we study the hierarchy of first-order spectra based on the number of variables. It has been conjectured that it collapses to three variables. We show the opposite: it forms an infinite hierarchy. However, despite the fact that more variables can express more spectra, we show that to establish whether the class of first-order spectra is closed under complement, it is sufficient to consider sentences using only three variables and binary relations.", acknowledgement = ack-nhfb, articleno = "17", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Kraus:2015:HHH, author = "Nicolai Kraus and Christian Sattler", title = "Higher Homotopies in a Hierarchy of Univalent Universes", journal = j-TOCL, volume = "16", number = "2", pages = "18:1--18:??", month = mar, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2729979", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 7 09:04:46 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "For Martin-L{\"o}f type theory with a hierarchy $ U_0 $: $ U_1 $: $ U_2 $: \ldots{} of univalent universes, we show that $ U_n $ is not an $n$-type. Our construction also solves the problem of finding a type that strictly has some high truncation level without using higher inductive types. In particular, $ U_n$ is such a type if we restrict it to $n$-types. We have fully formalized and verified our results within the dependently typed language and proof assistant Agda.", acknowledgement = ack-nhfb, articleno = "18", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Novakovic:2015:PSC, author = "Novak Novakovi{\'c} and Lutz Stra{\ss}burger", title = "On the Power of Substitution in the Calculus of Structures", journal = j-TOCL, volume = "16", number = "3", pages = "19:1--19:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2701424", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 7 09:04:47 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "There are two contributions in this article. First, we give a direct proof of the known fact that Frege systems with substitution can be p-simulated by the calculus of structures (CoS) extended with the substitution rule. This is done without referring to the p-equivalence of extended Frege systems and Frege systems with substitution. Second, we then show that the cut-free CoS with substitution is p-equivalent to the cut-free CoS with extension.", acknowledgement = ack-nhfb, articleno = "19", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Lazic:2015:NCB, author = "Ranko Lazi{\'c} and Sylvain Schmitz", title = "Nonelementary Complexities for Branching {VASS}, {MELL}, and Extensions", journal = j-TOCL, volume = "16", number = "3", pages = "20:1--20:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2733375", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 7 09:04:47 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We study the complexity of reachability problems on branching extensions of vector addition systems, which allows us to derive new non-elementary complexity bounds for fragments and variants of propositional linear logic. We show that provability in the multiplicative exponential fragment is T ower-hard already in the affine case-and hence non-elementary. We match this lower bound for the full propositional affine linear logic, proving its Tower-completeness. We also show that provability in propositional contractive linear logic is Ackermann-complete.", acknowledgement = ack-nhfb, articleno = "20", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Berkholz:2015:BQD, author = "Christoph Berkholz and Andreas Krebs and Oleg Verbitsky", title = "Bounds for the Quantifier Depth in Finite-Variable Logics: Alternation Hierarchy", journal = j-TOCL, volume = "16", number = "3", pages = "21:1--21:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2732409", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 7 09:04:47 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Given two structures $G$ and $H$ distinguishable in FO$^k$ (first-order logic with $k$ variables), let $ A^k(G, H)$ denote the minimum alternation depth of a FO$^k$ formula distinguishing $G$ from $H$. Let $ A^k(n)$ be the maximum value of $ A^k(G, H)$ over $n$-element structures. We prove the strictness of the quantifier alternation hierarchy of FO$^2$ in a strong quantitative form, namely $ A^2 (n) > n / 8 - 2$, which is tight up to a constant factor. For each $ k \geq 2$, it holds that $ A^k(n) > \log_{k + 1} n - 2$ even over colored trees, which is also tight up to a constant factor if $ k \geq 3$. For $ k \geq 3$, the last lower bound holds also over uncolored trees, whereas the alternation hierarchy of FO$^2$ collapses even over all uncolored graphs. We also show examples of colored graphs $G$ and $H$ on $n$ vertices that can be distinguished in FO$^2$ much more succinctly if the alternation number is increased just by one: Whereas in $ \Sigma_i$ it is possible to distinguish $G$ from $H$ with bounded quantifier depth, in $ \Pi_i$ this requires quantifier depth $ \Omega (n^2)$. The quadratic lower bound is best possible here because, if $G$ and $H$ can be distinguished in FO$^k$ with $i$ quantifier alternations, this can be done with quantifier depth $ n^{2 k - 2} + 1$ and the same number of alternations.", acknowledgement = ack-nhfb, articleno = "21", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Fazzinga:2015:CPA, author = "Bettina Fazzinga and Sergio Flesca and Francesco Parisi", title = "On the Complexity of Probabilistic Abstract Argumentation Frameworks", journal = j-TOCL, volume = "16", number = "3", pages = "22:1--22:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2749463", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 7 09:04:47 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Probabilistic abstract argumentation combines Dung's abstract argumentation framework with probability theory in order to model uncertainty in argumentation. In this setting, we address the fundamental problem of computing the probability that a set of arguments is an extension according to a given semantics. We focus on the most popular semantics (i.e., admissible, stable, complete, grounded, preferred, ideal-set, ideal, stage, and semistable) and show the following dichotomy result: computing the probability that a set of arguments is an extension is either FP or FP$^{\# P}$-complete depending on the semantics adopted. Our polynomial-time results are particularly interesting, as they hold for some semantics for which no polynomial-time technique was known so far.", acknowledgement = ack-nhfb, articleno = "22", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Lumsdaine:2015:LUM, author = "Peter Lefanu Lumsdaine and Michael A. Warren", title = "The Local Universes Model: an Overlooked Coherence Construction for Dependent Type Theories", journal = j-TOCL, volume = "16", number = "3", pages = "23:1--23:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2754931", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 7 09:04:47 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We present a new coherence theorem for comprehension categories, providing strict models of dependent type theory with all standard constructors, including dependent products, dependent sums, identity types, and other inductive types. Precisely, we take as input a ``weak model'': a comprehension category, equipped with structure corresponding to the desired logical constructions. We assume throughout that the base category is close to locally Cartesian closed: specifically, that products and certain exponentials exist. Beyond this, we require only that the logical structure should be weakly stable -a pure existence statement, not involving any specific choice of structure, weaker than standard categorical Beck--Chevalley conditions, and holding in the now standard homotopy-theoretic models of type theory. Given such a comprehension category, we construct an equivalent split one whose logical structure is strictly stable under reindexing. This yields an interpretation of type theory with the chosen constructors. The model is adapted from Voevodsky's use of universes for coherence, and at the level of fibrations is a classical construction of Giraud. It may be viewed in terms of local universes or delayed substitutions.", acknowledgement = ack-nhfb, articleno = "23", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Heule:2015:SAC, author = "Marijn J. H. Heule and Stefan Szeider", title = "A {SAT} Approach to Clique-Width", journal = j-TOCL, volume = "16", number = "3", pages = "24:1--24:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2736696", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 7 09:04:47 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Clique-width is a graph invariant that has been widely studied in combinatorics and computational logic. Computing the clique-width of a graph is an intricate problem, because the exact clique-width is not known even for very small graphs. We present a new method for computing clique-width via an encoding to propositional satisfiability (SAT), which is then evaluated by a SAT solver. Our encoding is based on a reformulation of clique-width in terms of partitions that utilizes an efficient encoding of cardinality constraints. Our SAT-based method is the first to discover the exact clique-width of various small graphs, including famous named graphs from the literature as well as random graphs of various density. With our method, we determined the smallest graphs that require a small predescribed clique-width. We further show how our method can be modified to compute the linear clique-width of graphs, a variant of clique-width that has recently received considerable attention. In an appendix, we provide certificates for tight upper bounds for the clique-width and linear clique-width of famous named graphs.", acknowledgement = ack-nhfb, articleno = "24", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Benerecetti:2015:RAS, author = "Massimo Benerecetti and Fabio Mogavero and Aniello Murano", title = "Reasoning About Substructures and Games", journal = j-TOCL, volume = "16", number = "3", pages = "25:1--25:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2757286", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 7 09:04:47 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Many decision problems in formal verification and design can be suitably formulated in game-theoretic terms. This is the case for the model checking of open and closed systems and both controller and reactive synthesis. Interpreted in this context, these problems require one to find a strategy (i.e., a plan) to force the system to fulfill some desired goal, no matter what the opponent (e.g., the environment) does. A strategy essentially constrains the possible behaviors of the system to those that are compatible with the decisions dictated by the plan itself. Therefore, finding a strategy to meet some goal basically reduces to identifying a portion of the model of interest (i.e., one of its substructures) that satisfies that goal. In this view, the ability to reason about substructures becomes a crucial aspect for several fundamental problems. In this article, we present and study a new branching-time temporal logic, called Substructure Temporal Logic (STL * for short), whose distinctive feature is to allow for quantifying over the possible substructure of a given structure. The logic is obtained by adding four new temporal-like operators to CTL *, whose interpretation is given relative to the partial order induced by a suitable substructure relation. STL * turns out to be very expressive and allows one to capture in a very natural way many well-known problems, such as module checking, reactive synthesis, and reasoning about games in a wide sense. A formal account of the model-theoretic properties of the new logic and results about (un)decidability and complexity of related decision problems are also provided.", acknowledgement = ack-nhfb, articleno = "25", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Asperti:2015:CCF, author = "Andrea Asperti", title = "Computational Complexity Via Finite Types", journal = j-TOCL, volume = "16", number = "3", pages = "26:1--26:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2764906", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 7 09:04:47 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We address computational complexity writing polymorphic functions between finite types (i.e., types with a finite number of canonical elements), expressing costs in terms of the cardinality of these types. This allows us to rediscover, in a more syntactical setting, the known result that the different levels in the hierarchy of higher-order primitive recursive functions (G{\"o}del system $T$), when interpreted over finite structures, precisely capture basic complexity classes: functions of rank 1 characterize LOGSPACE, rank 2 PTIME, rank 3 PSPACE, rank 4 EXPTIME = DTIME(2$^{poly}$), and so on.", acknowledgement = ack-nhfb, articleno = "26", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Hampson:2015:UPB, author = "Christopher Hampson and Agi Kurucz", title = "Undecidable Propositional Bimodal Logics and One-Variable First-Order Linear Temporal Logics with Counting", journal = j-TOCL, volume = "16", number = "3", pages = "27:1--27:??", month = jul, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2757285", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Fri Aug 7 09:04:47 MDT 2015", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "First-order temporal logics are notorious for their bad computational behavior. It is known that even the two-variable monadic fragment is highly undecidable over various linear timelines, and over branching time even one-variable fragments might be undecidable. However, there have been several attempts at finding well-behaved fragments of first-order temporal logics and related temporal description logics, mostly either by restricting the available quantifier patterns or by considering sub-Boolean languages. Here we analyze seemingly ``mild'' extensions of decidable one-variable fragments with counting capabilities, interpreted in models with constant, decreasing, and expanding first-order domains. We show that over most classes of linear orders, these logics are (sometimes highly) undecidable, even without constant and function symbols, and with the sole temporal operator ``eventually.'' We establish connections with bimodal logics over 2D product structures having linear and ``difference'' (inequality) component relations and prove our results in this bimodal setting. We show a general result saying that satisfiability over many classes of bimodal models with commuting ``unbounded'' linear and difference relations is undecidable. As a byproduct, we also obtain new examples of finitely axiomatizable but Kripke incomplete bimodal logics. Our results generalize similar lower bounds on bimodal logics over products of two linear relations, and our proof methods are quite different from the known proofs of these results. Unlike previous proofs that first ``diagonally encode'' an infinite grid and then use reductions of tiling or Turing machine problems, here we make direct use of the grid-like structure of product frames and obtain lower-complexity bounds by reductions of counter (Minsky) machine problems. Representing counter machine runs apparently requires less control over neighboring grid points than tilings or Turing machine runs, and so this technique is possibly more versatile, even if one component of the underlying product structures is ``close to'' being the universal relation.", acknowledgement = ack-nhfb, articleno = "27", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Filmus:2015:SSS, author = "Yuval Filmus and Massimo Lauria and Mladen Miksa and Jakob Nordstr{\"o}m and Marc Vinyals", title = "From Small Space to Small Width in Resolution", journal = j-TOCL, volume = "16", number = "4", pages = "28:1--28:??", month = nov, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2746339", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Jan 9 10:42:43 MST 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In 2003, Atserias and Dalmau resolved a major open question about the resolution proof system by establishing that the space complexity of a Conjunctive Normal Form (CNF) formula is always an upper bound on the width needed to refute the formula. Their proof is beautiful but uses a nonconstructive argument based on Ehrenfeucht-Fra{\"\i}ss{\'e} games. We give an alternative, more explicit, proof that works by simple syntactic manipulations of resolution refutations. As a by-product, we develop a ``black-box'' technique for proving space lower bounds via a ``static'' complexity measure that works against any resolution refutation-previous techniques have been inherently adaptive. We conclude by showing that the related question for polynomial calculus (i.e., whether space is an upper bound on degree) seems unlikely to be resolvable by similar methods.", acknowledgement = ack-nhfb, articleno = "28", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Cranen:2015:AFL, author = "Sjoerd Cranen and Maciej Gazda and Wieger Wesselink and Tim A. C. Willemse", title = "Abstraction in Fixpoint Logic", journal = j-TOCL, volume = "16", number = "4", pages = "29:1--29:??", month = nov, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2740964", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Jan 9 10:42:43 MST 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We present a theory of abstraction for the framework of parameterised Boolean equation systems, a first-order fixpoint logic. Parameterised Boolean equation systems can be used to solve a variety of problems in verification. We study the capabilities of the abstraction theory by comparing it to an abstraction theory for Generalised Kripke modal Transition Systems (GTSs). We show that for model checking the modal $\mu$-calculus, our abstractions can be exponentially more succinct than GTSs and our theory is as complete as the GTS framework for abstraction. Furthermore, we investigate the completeness of our theory irrespective of the encoded decision problem. We illustrate the potential of our theory through case studies using the first-order modal $\mu$-calculus and a real-time extension thereof, conducted using a prototype implementation of a new syntactic transformation for parameterised Boolean equation systems.", acknowledgement = ack-nhfb, articleno = "29", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Furusawa:2015:CDA, author = "Hitoshi Furusawa and Georg Struth", title = "Concurrent Dynamic Algebra", journal = j-TOCL, volume = "16", number = "4", pages = "30:1--30:??", month = nov, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2785967", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Jan 9 10:42:43 MST 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We reconstruct Peleg's concurrent dynamic logic in the context of modal Kleene algebras. We explore the algebraic structure of its multirelational semantics and develop an axiomatization of concurrent dynamic algebras from that basis. In this context, sequential composition is not associative. It interacts with parallel composition through a weak distributivity law. The modal operators of concurrent dynamic algebra are obtained from abstract axioms for domain and antidomain operators; the Kleene star is modelled as a least fixpoint. Algebraic variants of Peleg's axioms are shown to be derivable in these algebras, and their soundness is proved relative to the multirelational model. Additional results include iteration principles for the Kleene star and a refutation of variants of Segerberg's axiom in the multirelational setting. The most important results have been verified formally with Isabelle/HOL.", acknowledgement = ack-nhfb, articleno = "30", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Wang:2015:DLO, author = "Zhe Wang and Kewen Wang and Rodney Topor", title = "{DL-Lite} Ontology Revision Based on An Alternative Semantic Characterization", journal = j-TOCL, volume = "16", number = "4", pages = "31:1--31:??", month = nov, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2786759", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Jan 9 10:42:43 MST 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Ontology engineering and maintenance require (semi-)automated ontology change operations. Intensive research has been conducted on TBox and ABox changes in description logics (DLs), and various change operators have been proposed in the literature. Existing operators largely fall into two categories: syntax-based and model-based. While each approach has its advantages and disadvantages, an important topic that has rarely been explored is how to achieve a balance between syntax-based and model-based approaches. Also, most existing operators are specially designed for either TBox change or ABox change, and cannot handle the general ontology revision task-given a DL knowledge base (KB, a pair consisting of a TBox and an ABox), how to revise it by a set of TBox and ABox axioms ( i.e., a new DL KB). In this article, we introduce an alternative structure for DL-Lite, called a featured interpretation, and show that featured models provide a finite and tight characterization to the classical semantics of DL-Lite. A key issue for defining a change operator is the so-called expressibility, that is, whether a set of models (or featured models here) is axiomatizable in DLs. It is indeed much easier to obtain expressibility results for featured models than for classical DL models. As a result, the new semantics determined by featured models provides a method for defining and studying various changes of DL-Lite KBs that involve both TBoxes and ABoxes. To demonstrate the usefulness of the new semantic characterization in ontology change, we define two revision operators for DL-Lite KBs using featured models and study their properties. In particular, we show that our two operators both satisfy AGM postulates. We show that the complexity of our revisions is $\Pi^P_2$-complete, that is, on the same level as major revision operators in propositional logic, which further justifies the feasibility of our revision approach for DL-Lite. Also, we develop algorithms for these DL-Lite revisions.", acknowledgement = ack-nhfb, articleno = "31", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Schwartz:2015:DRS, author = "Daniel G. Schwartz", title = "Dynamic Reasoning Systems", journal = j-TOCL, volume = "16", number = "4", pages = "32:1--32:??", month = nov, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2798727", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Jan 9 10:42:43 MST 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "A dynamic reasoning system (DRS) is an adaptation of a conventional formal logical system that explicitly portrays reasoning as a temporal activity, with each extralogical input to the system and each inference rule application being viewed as occurring at a distinct timestep. Every DRS incorporates some well-defined logic together with a controller that serves to guide the reasoning process in response to user inputs. Logics are generic, whereas controllers are application specific. Every controller does, nonetheless, provide an algorithm for nonmonotonic belief revision. The general notion of a DRS comprises a framework within which one can formulate the logic and algorithms for a given application and prove that the algorithms are correct, that is, that they serve to (1) derive all salient information and (2) preserve the consistency of the belief set. This article illustrates the idea with ordinary first-order predicate calculus, suitably modified for the present purpose, and two examples. The latter example revisits some classic nonmonotonic reasoning puzzles (Opus the Penguin, Nixon Diamond) and shows how these can be resolved in the context of a DRS, using an expanded version of first-order logic that incorporates typed predicate symbols. All concepts are rigorously defined and effectively computable, thereby providing the foundation for a future software implementation.", acknowledgement = ack-nhfb, articleno = "32", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Marchioni:2015:LGL, author = "Enrico Marchioni and Michael Wooldridge", title = "{Lukasiewicz} Games: a Logic-Based Approach to Quantitative Strategic Interactions", journal = j-TOCL, volume = "16", number = "4", pages = "33:1--33:??", month = nov, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2783436", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Jan 9 10:42:43 MST 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Boolean games provide a simple, compact, and theoretically attractive abstract model for studying multiagent interactions in settings where players will act strategically in an attempt to achieve individual goals. A standard critique of Boolean games, however, is that the strictly dichotomous nature of the preference relations induced by Boolean goals inevitably trivialises the nature of such strategic interactions: a player is assumed to be indifferent between all outcomes that satisfy her goal, and indifferent between all outcomes that do not satisfy her goal. While various proposals have been made to overcome this limitation, many of these proposals require the inclusion of nonlogical structures into games to capture nondichotomous preferences. In this article, we introduce Lukasiewicz games, which overcome this limitation by allowing goals to be specified using Lukasiewicz logics. By expressing goals as formulae of Lukasiewicz logics, we can express a much richer class of utility functions for players than is possible using classical Boolean logic: we can express every continuous piecewise linear polynomial function with rational coefficients over [0, 1]$^n$ as well as their finite-valued restrictions over {0, 1/ k, ..., ( k --- 1)/ k, 1}$^n$. We thus obtain a representation of nondichotomous preference structures within a purely logical framework. After introducing the formal framework of Lukasiewicz games, we present a number of detailed worked examples to illustrate the framework, and then investigate some of their theoretical properties. In particular, we present a logical characterisation of the existence of Nash equilibria in finite and infinite Lukasiewicz games. We conclude by briefly discussing issues of computational complexity.", acknowledgement = ack-nhfb, articleno = "33", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Friedmann:2015:RBI, author = "Oliver Friedmann and Felix Klaedtke and Martin Lange", title = "{Ramsey}-Based Inclusion Checking for Visibly Pushdown Automata", journal = j-TOCL, volume = "16", number = "4", pages = "34:1--34:??", month = nov, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2774221", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Jan 9 10:42:43 MST 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Checking whether one formal language is included in another is important in many verification tasks. In this article, we provide solutions for checking the inclusion of languages given by visibly pushdown automata over both finite and infinite words. Visibly pushdown automata are a richer automaton model than the classical finite-state automata, which allows one, for example, to reason about the nesting of procedure calls in the executions of recursive imperative programs. The presented solutions do not rely on explicit automaton constructions for determinization and complementation. Instead, they are more direct and generalize the so-called Ramsey-based inclusion-checking algorithms, which apply to classical finite-state automata and proved to be effective there to visibly pushdown automata. We also experimentally evaluate these algorithms, demonstrating the virtues of avoiding explicit determinization and complementation constructions.", acknowledgement = ack-nhfb, articleno = "34", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Kramer:2015:LII, author = "Simon Kramer", title = "Logic of Intuitionistic Interactive Proofs (Formal Theory of Perfect Knowledge Transfer)", journal = j-TOCL, volume = "16", number = "4", pages = "35:1--35:??", month = nov, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2811263", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Jan 9 10:42:43 MST 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We produce a decidable super-intuitionistic normal modal logic of internalised intuitionistic (and thus disjunctive and monotonic) interactive proofs (LIiP) from an existing classical counterpart of classical monotonic non-disjunctive interactive proofs (LiP). Intuitionistic interactive proofs effect a durable epistemic impact in the possibly adversarial communication medium CM (which is imagined as a distinguished agent) and only in that, that consists in the permanent induction of the perfect and thus disjunctive knowledge of their proof goal by means of CM's knowledge of the proof: If CM knew my proof then CM would persistently and also disjunctively know that my proof goal is true. So intuitionistic interactive proofs effect a lasting transfer of disjunctive propositional knowledge (disjunctively knowable facts) in the communication medium of multi-agent distributed systems via the transmission of certain individual knowledge (knowable intuitionistic proofs). Our (necessarily) CM-centred notion of proof is also a disjunctive explicit refinement of KD45-belief, and yields also such a refinement of standard S5-knowledge. Monotonicity but not communality is a commonality of LiP, LIiP, and their internalised notions of proof. As a side-effect, we offer a short internalised proof of the Disjunction Property of Intuitionistic Logic (originally proved by G{\"o}del).", acknowledgement = ack-nhfb, articleno = "35", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Carayol:2015:ERA, author = "Arnaud Carayol and Axel Haddad and Olivier Serre", title = "Erratum for {``Randomization in Automata on Infinite Trees''}", journal = j-TOCL, volume = "16", number = "4", pages = "36:1--36:??", month = nov, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2824254", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Jan 9 10:42:43 MST 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", acknowledgement = ack-nhfb, articleno = "36", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Platzer:2015:DGL, author = "Andr{\'e} Platzer", title = "Differential Game Logic", journal = j-TOCL, volume = "17", number = "1", pages = "1:1--1:??", month = dec, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2817824", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Jan 9 10:42:43 MST 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Differential game logic (dG L ) is a logic for specifying and verifying properties of hybrid games, i.e., games that combine discrete, continuous, and adversarial dynamics. Unlike hybrid systems, hybrid games allow choices in the system dynamics to be resolved adversarially by different players with different objectives. The logic dG L can be used to study the existence of winning strategies for such hybrid games, i.e., ways of resolving the player's choices in some way so that he wins by achieving his objective for all choices of the opponent. Hybrid games are determined, i.e., from each state, one player has a winning strategy, yet computing their winning regions may take transfinitely many steps. The logic dG L, nevertheless, has a sound and complete axiomatization relative to any expressive logic. Separating axioms are identified that distinguish hybrid games from hybrid systems. Finally, dG L is proved to be strictly more expressive than the corresponding logic of hybrid systems by characterizing the expressiveness of both.", acknowledgement = ack-nhfb, articleno = "1", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Michaliszyn:2015:DEM, author = "Jakub Michaliszyn and Jan Otop and Emanuel Kiero{\'n}ski", title = "On the Decidability of Elementary Modal Logics", journal = j-TOCL, volume = "17", number = "1", pages = "2:1--2:??", month = dec, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2817825", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Jan 9 10:42:43 MST 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We consider the satisfiability problem for modal logic over first-order definable classes of frames. We confirm the conjecture from Hemaspaandra and Schnoor [2008] that modal logic is decidable over classes definable by universal Horn formulae. We provide a full classification of Horn formulae with respect to the complexity of the corresponding satisfiability problem. It turns out, that except for the trivial case of inconsistent formulae, local satisfiability is either NP-complete or PS pace-complete, and global satisfiability is NP-complete, PSpace-complete, or ExpTime-complete. We also show that the finite satisfiability problem for modal logic over Horn definable classes of frames is decidable. On the negative side, we show undecidability of two related problems. First, we exhibit a simple universal three-variable formula defining the class of frames over which modal logic is undecidable. Second, we consider the satisfiability problem of bimodal logic over Horn definable classes of frames, and also present a formula leading to undecidability.", acknowledgement = ack-nhfb, articleno = "2", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Chretien:2015:SPP, author = "R{\'e}my Chr{\'e}tien and V{\'e}ronique Cortier and St{\'e}phanie Delaune", title = "From Security Protocols to Pushdown Automata", journal = j-TOCL, volume = "17", number = "1", pages = "3:1--3:??", month = dec, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2811262", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Jan 9 10:42:43 MST 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Formal methods have been very successful in analyzing security protocols for reachability properties such as secrecy or authentication. In contrast, there are very few results for equivalence-based properties, crucial for studying, for example, privacy-like properties such as anonymity or vote secrecy. We study the problem of checking equivalence of security protocols for an unbounded number of sessions. Since replication leads very quickly to undecidability (even in the simple case of secrecy), we focus on a limited fragment of protocols (standard primitives but pairs, one variable per protocol's rules) for which the secrecy preservation problem is known to be decidable. Surprisingly, this fragment turns out to be undecidable for equivalence. Then, restricting our attention to deterministic protocols, we propose the first decidability result for checking equivalence of protocols for an unbounded number of sessions. This result is obtained through a characterization of equivalence of protocols in terms of equality of languages of (generalized, real-time) deterministic pushdown automata. We further show that checking for equivalence of protocols is actually equivalent to checking for equivalence of generalized, real-time deterministic pushdown automata. Very recently, the algorithm for checking for equivalence of deterministic pushdown automata has been implemented. We have implemented our translation from protocols to pushdown automata, yielding the first tool that decides equivalence of (some class of) protocols, for an unbounded number of sessions. As an application, we have analyzed some protocols of the literature including a simplified version of the basic access control (BAC) protocol used in biometric passports.", acknowledgement = ack-nhfb, articleno = "3", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Cerrito:2015:OTM, author = "Serenella Cerrito and Am{\'e}lie David and Valentin Goranko", title = "Optimal Tableau Method for Constructive Satisfiability Testing and Model Synthesis in the Alternating-Time Temporal Logic {ATL+}", journal = j-TOCL, volume = "17", number = "1", pages = "4:1--4:??", month = dec, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2811261", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Jan 9 10:42:43 MST 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We develop a sound, complete, and practically implementable tableau-based decision method for constructive satisfiability testing and model synthesis for the fragment ATL$^+$ of the full alternating-time temporal logic ALT$^*$. The method extends in an essential way a previously developed tableau-based decision method for ATL and works in 2EXPTIME, which is the optimal worst-case complexity of the satisfiability problem for ATL$^+$. We also discuss how suitable parameterizations and syntactic restrictions on the class of input ATL$^+$ formulas can reduce the complexity of the satisfiability problem.", acknowledgement = ack-nhfb, articleno = "4", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Rabe:2015:LTM, author = "Florian Rabe", title = "{Lax} Theory Morphisms", journal = j-TOCL, volume = "17", number = "1", pages = "5:1--5:??", month = dec, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2818644", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Jan 9 10:42:43 MST 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "When relating formal languages, e.g., in logic or type theory, it is often important to establish representation theorems. These interpret one language in terms of another in a way that preserves semantic properties such as provability or typing. Metalanguages for stating representation theorems can be divided into two groups: First, computational languages are very expressive (usually Turing-complete), but verifying the representation theorems is very difficult (often prohibitively so); second, declarative languages are restricted to certain classes of representation theorems (often based on theory morphisms), for which correctness is decidable. Neither is satisfactory, and this article contributes to the investigation of the trade-off between these two methods. Concretely, we introduce lax theory morphisms, which combine some of the advantages of each: they are substantially more expressive than conventional theory morphisms, but they share many of the invariants that make theory morphisms easy to work with. Specifically, we introduce lax morphisms between theories of a dependently typed logical framework, but our approach and results carry over to most declarative metalanguages. We demonstrate the usefulness of lax theory morphisms by stating and verifying a type erasure translation from typed to untyped first-order logic. The translation is stated as a single lax theory morphism, and the invariants of the framework guarantee its correctness. This is the first time such a complex translation has be verified in a declarative framework.", acknowledgement = ack-nhfb, articleno = "5", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Leino:2015:APS, author = "K. Rustan M. Leino and Paqui Lucio", title = "An Assertional Proof of the Stability and Correctness of {Natural Mergesort}", journal = j-TOCL, volume = "17", number = "1", pages = "6:1--6:22", month = dec, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2814571", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Jan 9 10:42:43 MST 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/java2010.bib; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We present a mechanically verified implementation of the sorting algorithm Natural Mergesort that consists of a few methods specified by their contracts of pre/post conditions. Methods are annotated with assertions that allow the automatic verification of the contract satisfaction. This program-proof is made using the state-of-the-art verifier Dafny. We verify not only the standard sortedness property, but also that the algorithm performs a stable sort. Throughout the article, we provide and explain the complete text of the program-proof.", acknowledgement = ack-nhfb, articleno = "6", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", remark = "From the conclusion on pages 20--21: ``There is no doubt that sorting algorithms are useful and important in software. Good algorithms based on ingenious ideas can be subtle and warrant formal proofs. Indeed, if the comparison {\tt GT(min,xs.head)} in function {\tt descending} were replaced by {\tt $ \neg $GT(xs.head,min)}, then the algorithm would no longer be stable. An excellent example is the recent revelation [de Gouw et al. 2015] of the incorrectness of a very popular sorting algorithm that has been running since 2002 in billions of computers, cloud services, and mobile phones. Indeed, it is the default sorting algorithm for Android SDK, Sun's JDK, and OpenJDK. The bug was discovered and fixed using the formal verification tool KeY [Beckert et al. 2007]. The bug appeared already in the original implementation in Python.'' The 2015 reference is ``Stijn de Gouw, Jurriaan Rot, Frank S. de Boer, Richard Bubel, and Reiner H{\"a}hnle. 2015. \booktitle{OpenJDK's {\tt java.utils.Collection.sort()} is broken: The good, the bad and the worst case}. In \booktitle{Computer Aided Verification. 27th International Conference, CAV 2015} (LNCS). Springer. doi:10.1007/978-3-319-21690-4_16.''", } @Article{Fichte:2015:BND, author = "Johannes K. Fichte and Stefan Szeider", title = "Backdoors to Normality for Disjunctive Logic Programs", journal = j-TOCL, volume = "17", number = "1", pages = "7:1--7:??", month = dec, year = "2015", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2818646", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Sat Jan 9 10:42:43 MST 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The main reasoning problems for disjunctive logic programs are complete for the second level of the polynomial hierarchy and hence considered harder than the same problems for normal (i.e., disjunction-free) programs, which are on the first level. We propose a new exact method for solving the disjunctive problems which exploits the small distance of a disjunctive programs from being normal. The distance is measured in terms of the size of a smallest ``backdoor to normality,'' which is the smallest number of atoms whose deletion makes the program normal. Our method consists of three phases. In the first phase, a smallest backdoor is computed. We show that this can be done using an efficient algorithm for computing a smallest vertex cover of a graph. In the second phase, the backdoor is used to transform the logic program into a quantified Boolean formula (QBF) where the number of universally quantified variables equals the size of the backdoor and where the total size of the quantified Boolean formula is quasilinear in the size of the given logic program. The quasilinearity is achieved by means of a characterization of the least model of a Horn program in terms of level numberings. In a third phase, the universal variables are eliminated using universal expansion yielding a propositional formula. The blowup in the last phase is confined to a factor that is exponential in the size of the backdoor but linear in the size of the quantified Boolean formula. By checking the satisfiability of the resulting formula with a S at solver (or by checking the satisfiability of the quantified Boolean formula by a Qbf-Sat solver), we can decide the Asp reasoning problems on the input program. In consequence, we have a transformation from Asp problems to propositional satisfiability where the combinatorial explosion, which is expected when transforming a problem from the second level of the polynomial hierarchy to the first level, is confined to a function of the distance to normality of the input program. In terms of parameterized complexity, the transformation is fixed-parameter tractable. We complement this result by showing that (under plausible complexity-theoretic assumptions) such a fixed-parameter tractable transformation is not possible if we consider the distance to tightness instead of distance to normality.", acknowledgement = ack-nhfb, articleno = "7", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Benedikt:2016:EIP, author = "Michael Benedikt and Balder {Ten Cate} and Michael {Vanden Boom}", title = "Effective Interpolation and Preservation in Guarded Logics", journal = j-TOCL, volume = "17", number = "2", pages = "8:1--8:??", month = mar, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2814570", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Jun 20 09:19:30 MDT 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Desirable properties of a logic include decidability, and a model theory that inherits properties of first-order logic, such as interpolation and preservation theorems. It is known that the Guarded Fragment (GF) of first-order logic is decidable and satisfies some preservation properties from first-order model theory; however, it fails to have Craig interpolation. The Guarded Negation Fragment (GNF), a recently defined extension, is known to be decidable and to have Craig interpolation. Here we give the first results on effective interpolation for extensions of GF. We provide an interpolation procedure for GNF whose complexity matches the doubly exponential upper bound for satisfiability of GNF. We show that the same construction gives not only Craig interpolation, but Lyndon interpolation and relativized interpolation, which can be used to provide effective proofs of some preservation theorems. We provide upper bounds on the size of GNF interpolants for both GNF and GF input, and complement this with matching lower bounds.", acknowledgement = ack-nhfb, articleno = "8", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Liberatore:2016:BME, author = "Paolo Liberatore", title = "Belief Merging by Examples", journal = j-TOCL, volume = "17", number = "2", pages = "9:1--9:??", month = mar, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2818645", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Jun 20 09:19:30 MDT 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "A common assumption in belief revision is that the reliability of the information sources is either given, derived from temporal information, or the same for all. This article does not describe a new semantics for integration but studies the problem of obtaining the reliability of the sources given the result of a previous merging. As an example, corrections performed manually on the result of merging some databases may indicate that the relative reliability of their sources is different from what was previously assumed, helping subsequent data mergings.", acknowledgement = ack-nhfb, articleno = "9", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bova:2016:MCE, author = "Simone Bova and Robert Ganian and Stefan Szeider", title = "Model Checking Existential Logic on Partially Ordered Sets", journal = j-TOCL, volume = "17", number = "2", pages = "10:1--10:??", month = mar, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2814937", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Jun 20 09:19:30 MDT 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We study the problem of checking whether an existential sentence (i.e., a first-order sentence in prefix form built using existential quantifiers and all Boolean connectives) is true in a finite partially ordered set (a poset). A poset is a reflexive, antisymmetric, and transitive digraph. The problem encompasses the fundamental embedding problem of finding an isomorphic copy of a poset as an induced substructure of another poset. Model checking existential logic is already NP-hard on a fixed poset; thus, we investigate structural properties of posets yielding conditions for fixed-parameter tractability when the problem is parameterized by the sentence. We identify width as a central structural property (the width of a poset is the maximum size of a subset of pairwise incomparable elements); our main algorithmic result is that model checking existential logic on classes of finite posets of bounded width is fixed-parameter tractable. We observe a similar phenomenon in classical complexity, in which we prove that the isomorphism problem is polynomial-time tractable on classes of posets of bounded width; this settles an open problem in order theory. We surround our main algorithmic result with complexity results on less restricted, natural neighboring classes of finite posets, establishing its tightness in this sense. We also relate our work with (and demonstrate its independence of) fundamental fixed-parameter tractability results for model checking on digraphs of bounded degree and bounded clique-width.", acknowledgement = ack-nhfb, articleno = "10", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Albert:2016:MHP, author = "Elvira Albert and Antonio Flores-Montoya and Samir Genaim and Enrique Martin-Martin", title = "May-Happen-in-Parallel Analysis for Actor-Based Concurrency", journal = j-TOCL, volume = "17", number = "2", pages = "11:1--11:??", month = mar, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2824255", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Jun 20 09:19:30 MDT 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "This article presents a may-happen-in-parallel (MHP) analysis for languages with actor-based concurrency. In this concurrency model, actors are the concurrency units such that, when a method is invoked on an actor $a_2$ from a task executing on actor $a_1$, statements of the current task in $a_1$ may run in parallel with those of the (asynchronous) call on $a_2$, and with those of transitively invoked methods. The goal of the MHP analysis is to identify pairs of statements in the program that may run in parallel in any execution. Our MHP analysis is formalized as a method-level ( local ) analysis whose information can be modularly composed to obtain application-level ( global ) information. The information yielded by the MHP analysis is essential to infer more complex properties of actor-based concurrent programs, for example, data race detection, deadlock freeness, termination, and resource consumption analyses can greatly benefit from the MHP relations to increase their accuracy. We report on MayPar, a prototypical implementation of an MHP static analyzer for a distributed asynchronous language.", acknowledgement = ack-nhfb, articleno = "11", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Demri:2016:ECS, author = "Stephane Demri and Morgan Deters", title = "Expressive Completeness of Separation Logic with Two Variables and No Separating Conjunction", journal = j-TOCL, volume = "17", number = "2", pages = "12:1--12:??", month = mar, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2835490", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Jun 20 09:19:30 MDT 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Separation logic is used as an assertion language for Hoare-style proof systems about programs with pointers, and there is an ongoing quest for understanding its complexity and expressive power. Herein, we show that first-order separation logic with one record field restricted to two variables and the separating implication (no separating conjunction) is as expressive as weak second-order logic, substantially sharpening a previous result. Capturing weak second-order logic with such a restricted form of separation logic requires substantial updates to known proof techniques. We develop these and, as a by-product, identify the smallest fragment of separation logic known to be undecidable: first-order separation logic with one record field, two variables, and no separating conjunction. Because we forbid ourselves the use of many syntactic resources, this underscores even further the power of separating implication on concrete heaps.", acknowledgement = ack-nhfb, articleno = "12", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Mamouras:2016:HLD, author = "Konstantinos Mamouras", title = "The {Hoare} Logic of Deterministic and Nondeterministic Monadic Recursion Schemes", journal = j-TOCL, volume = "17", number = "2", pages = "13:1--13:??", month = mar, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2835491", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Jun 20 09:19:30 MDT 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The equational theory of deterministic monadic recursion schemes is known to be decidable by the result of S{\'e}nizergues on the decidability of the problem of DPDA equivalence. In order to capture some properties of the domain of computation, we augment equations with certain hypotheses. This preserves the decidability of the theory, which we call simple implicational theory. The asymptotically fastest algorithm known for deciding the equational theory, and also for deciding the simple implicational theory, has a running time that is nonelementary. We therefore consider a restriction of the properties about schemes to check: instead of arbitrary equations $ f \equiv g $ between schemes, we focus on propositional Hoare assertions $ \{ p \} f \{ q \} $, where $f$ is a scheme and $p$, $q$ are tests. Such Hoare assertions have a straightforward encoding as equations. For this subclass of program properties, we can also handle nondeterminism at the syntactic and/or at the semantic level, without increasing the complexity of the theories. We investigate the Hoare theory of monadic recursion schemes, that is, the set of valid implications whose conclusions are Hoare assertions and whose premises are of a certain simple form. We present a sound and complete Hoare-style calculus for this theory. We also show that the Hoare theory can be decided in exponential time, and that it is complete for this class.", acknowledgement = ack-nhfb, articleno = "13", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Benedikt:2016:LUO, author = "Michael Benedikt and Clemens Ley", title = "Limiting Until in Ordered Tree Query Languages", journal = j-TOCL, volume = "17", number = "2", pages = "14:1--14:??", month = mar, year = "2016", CODEN = "????", DOI = "http://dx.doi.org/10.1145/2856104", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Mon Jun 20 09:19:30 MDT 2016", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Marx and de Rijke have shown that the navigational core of the w3c XML query language XPath is not first-order complete; that is, it cannot express every query definable in first-order logic over the navigational predicates. How can one extend XPath to get a first-order complete language? Marx has shown that Conditional XPath-an extension of XPath with an ``Until'' operator-is first-order complete. The completeness argument makes essential use of the presence of upward axes in Conditional XPath. We examine whether it is possible to get ``forward-only'' languages that are first-order complete for Boolean queries on ordered trees. It is easy to see that a variant of the temporal logic CTL$^*$ is first-order complete; the variant has path quantifiers for downward, leftward, and rightward paths, while along a path one can check arbitrary formulas of Linear Temporal Logic (LTL). This language has two major disadvantages: It requires path quantification in both horizontal directions (in particular, it requires looking backward at the prior siblings of a node), and it requires the consideration of formulas of LTL of arbitrary complexity on vertical paths. This last is in contrast with Marx's Conditional XPath, which requires only the checking of a single Until operator on a path. We investigate whether either of these restrictions can be eliminated. Our main results are negative ones. We show that if we restrict our CTL$^*$ language by having an Until operator in only one horizontal direction, then we lose completeness. We also show that no restriction to a ``small'' subset of LTL along vertical paths is sufficient for first-order completeness. Smallness here means of bounded ``Until Depth,'' a measure of complexity of LTL formulas defined by Etessami and Wilke. In particular, it follows from our work that Conditional XPath with only forward axes is not expressively complete; this extends results proved by Rabinovich and Maoz in the context of infinite unordered trees.", acknowledgement = ack-nhfb, articleno = "14", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Dongol:2016:CUC, author = "Brijesh Dongol and Ian J. Hayes and Georg Struth", title = "Convolution as a Unifying Concept: Applications in Separation Logic, Interval Calculi, and Concurrency", journal = j-TOCL, volume = "17", number = "3", pages = "15:1--15:??", month = jul, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2874773", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:13 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "A notion of convolution is presented in the context of formal power series together with lifting constructions characterising algebras of such series, which usually are quantales. A number of examples underpin the universality of these constructions, the most prominent ones being separation logics, where convolution is separating conjunction in an assertion quantale; interval logics, where convolution is the chop operation; and stream interval functions, where convolution is proposed for analysing the trajectories of dynamical or real-time systems. A Hoare logic can be constructed in a generic fashion on the power-series quantale, which applies to each of these examples. In many cases, commutative notions of convolution have natural interpretations as concurrency operations.", acknowledgement = ack-nhfb, articleno = "15", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Lazic:2016:ZHH, author = "Ranko Lazi{\'c} and Jo{\"e}l Ouaknine and James Worrell", title = "{Zeno}, {Hercules}, and the {Hydra}: Safety Metric Temporal Logic is {Ackermann}-Complete", journal = j-TOCL, volume = "17", number = "3", pages = "16:1--16:??", month = jul, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2874774", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:13 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Metric temporal logic (MTL) is one of the most prominent specification formalisms for real-time systems. Over infinite timed words, full MTL is undecidable, but satisfiability for a syntactially defined safety fragment, called safety MTL, was proved decidable several years ago. Satisfiability for safety MTL is also known to be equivalent to a fair termination problem for a class of channel machines with insertion errors. However, hitherto, its precise computational complexity has remained elusive, with only a nonelementary lower bound. Via another equivalent problem, namely termination for a class of rational relations, we show that satisfiability for safety MTL is Ackermann-complete (i.e., among the easiest nonprimitive recursive problems). This is surprising since decidability was originally established using Higman's Lemma, suggesting a much higher nonmultiply recursive complexity.", acknowledgement = ack-nhfb, articleno = "16", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Ciabattoni:2016:PLS, author = "Agata Ciabattoni and Revantha Ramanayake", title = "Power and Limits of Structural Display Rules", journal = j-TOCL, volume = "17", number = "3", pages = "17:1--17:??", month = jul, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2874775", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:13 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "What can (and cannot) be expressed by structural display rules? Given a display calculus, we present a systematic procedure for transforming axioms into structural rules. The conditions for the procedure are given in terms of (purely syntactic) abstract properties of the base calculus; thus, the method applies to large classes of calculi and logics. If the calculus satisfies certain additional properties, we prove the converse direction, thus characterising the class of axioms that can be captured by structural display rules. Determining if an axiom belongs to this class or not is shown to be decidable. Applied to the display calculus for tense logic, we obtain a new proof of Kracht's Display Theorem I.", acknowledgement = ack-nhfb, articleno = "17", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Drabent:2016:CCL, author = "Wlodzimierz Drabent", title = "Correctness and Completeness of Logic Programs", journal = j-TOCL, volume = "17", number = "3", pages = "18:1--18:??", month = jul, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2898434", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:13 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We discuss proving correctness and completeness of definite clause logic programs. We propose a method for proving completeness, while for proving correctness we employ a method that should be well known but is often neglected. Also, we show how to prove completeness and correctness in the presence of SLD-tree pruning, and point out that approximate specifications simplify specifications and proofs. We compare the proof methods to declarative diagnosis (algorithmic debugging), showing that approximate specifications eliminate a major drawback of the latter. We argue that our proof methods reflect natural declarative thinking about programs, and that they can be used, formally or informally, in everyday programming.", acknowledgement = ack-nhfb, articleno = "18", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Atserias:2016:NPM, author = "Albert Atserias and Massimo Lauria and Jakob Nordstr{\"o}m", title = "Narrow Proofs May Be Maximally Long", journal = j-TOCL, volume = "17", number = "3", pages = "19:1--19:??", month = jul, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2898435", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:13 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We prove that there are 3-CNF formulas over n variables that can be refuted in resolution in width $w$ but require resolution proofs of size $ n^{\Omega (w)}$. This shows that the simple counting argument that any formula refutable in width w must have a proof in size $ n^{O(w)}$ is essentially tight. Moreover, our lower bound generalizes to polynomial calculus resolution and Sherali--Adams, implying that the corresponding size upper bounds in terms of degree and rank are tight as well. The lower bound does not extend all the way to Lasserre, however, since we show that there the formulas we study have proofs of constant rank and size polynomial in both $n$ and $w$.", acknowledgement = ack-nhfb, articleno = "19", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Creignou:2016:BMW, author = "Nadia Creignou and Odile Papini and Stefan R{\"u}mmele and Stefan Woltran", title = "Belief Merging within Fragments of Propositional Logic", journal = j-TOCL, volume = "17", number = "3", pages = "20:1--20:??", month = jul, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2898436", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:13 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Recently, belief change within the framework of fragments of propositional logic has gained increasing attention. Previous research focused on belief contraction and belief revision on the Horn fragment. However, the problem of belief merging within fragments of propositional logic has been mostly neglected so far. We present a general approach to defining new merging operators derived from existing ones such that the result of merging remains in the fragment under consideration. Our approach is not limited to the case of Horn fragment; it is applicable to any fragment of propositional logic characterized by a closure property on the sets of models of its formul{\ae}. We study the logical properties of the proposed operators regarding satisfaction of merging postulates, considering, in particular, distance-based merging operators for Horn and Krom fragments.", acknowledgement = ack-nhfb, articleno = "20", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Trybus:2016:RRB, author = "Adam Trybus", title = "Rational Region-Based Affine Logic of the Real Plane", journal = j-TOCL, volume = "17", number = "3", pages = "21:1--21:??", month = jul, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2897190", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:13 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The region-based spatial logics, where variables are set to range over certain subsets of geometric space, are the focal point of the qualitative spatial reasoning, a subfield of the KR\&R research area. A lot of attention has been devoted to developing the topological spatial logics, leaving other systems relatively underexplored. We are concerned with a specific example of a region-based affine spatial logic. Building on the previous results on spatial logics with convexity, we axiomatise the theory of $ M = \langle R O Q(R^2), {\rm conv}^M, \leq^M \rangle $, where $ R O Q(R^2) $ is the set of regular open rational polygons of the real plane; $ {\rm conv}^M $ is the convexity property and $ l e q^M $ is the inclusion relation. The axiomatisation uses two infinitary rules of inference and a number of axiom schemas.", acknowledgement = ack-nhfb, articleno = "21", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Wen:2016:MPT, author = "Lian Wen and Kewen Wang and Yi-Dong Shen and Fangzhen Lin", title = "A Model for Phase Transition of Random Answer-Set Programs", journal = j-TOCL, volume = "17", number = "3", pages = "22:1--22:??", month = jul, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2926791", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:13 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "The critical behaviors of NP-complete problems have been studied extensively, and numerous results have been obtained for Boolean formula satisfiability (SAT) and constraint satisfaction (CSP), among others. However, few results are known for the critical behaviors of NP-hard nonmonotonic reasoning problems so far; in particular, a mathematical model for phase transition in nonmonotonic reasoning is still missing. In this article, we investigate the phase transition of negative two-literal logic programs under the answer-set semantics. We choose this class of logic programs since it is the simplest class for which the consistency problem of deciding if a program has an answer set is still NP-complete. We first introduce a new model, called quadratic model for generating random logic programs in this class. We then mathematically prove that the consistency problem for this class of logic programs exhibits a phase transition. Furthermore, the phase-transition follows an easy-hard-easy pattern. Given the correspondence between answer sets for negative two-literal programs and kernels for graphs, as a corollary, our result significantly generalizes de la Vega's well-known theorem for phase transition on the existence of kernels in random graphs. We also report some experimental results. Given our mathematical results, these experimental results are not really necessary. We include them here as they suggest that our phase-transition result is more general and likely holds for more general classes of logic programs.", acknowledgement = ack-nhfb, articleno = "22", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Chadha:2016:AVE, author = "Rohit Chadha and Vincent Cheval and Stefan Ciob{\^a}ca and Steve Kremer", title = "Automated Verification of Equivalence Properties of Cryptographic Protocols", journal = j-TOCL, volume = "17", number = "4", pages = "23:1--23:??", month = nov, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2926715", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:14 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/cryptography2010.bib; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Indistinguishability properties are essential in formal verification of cryptographic protocols. They are needed to model anonymity properties, strong versions of confidentiality, and resistance against offline guessing attacks. Indistinguishability properties can be conveniently modeled as equivalence properties. We present a novel procedure to verify equivalence properties for a bounded number of sessions of cryptographic protocols. As in the applied pi calculus, our protocol specification language is parametrized by a first-order sorted term signature and an equational theory that allows formalization of algebraic properties of cryptographic primitives. Our procedure is able to verify trace equivalence for determinate cryptographic protocols. On determinate protocols, trace equivalence coincides with observational equivalence, which can therefore be automatically verified for such processes. When protocols are not determinate, our procedure can be used for both under- and over-approximations of trace equivalence, which proved successful on examples. The procedure can handle a large set of cryptographic primitives, namely those whose equational theory is generated by an optimally reducing convergent rewrite system. The procedure is based on a fully abstract modelling of the traces of a bounded number of sessions of the protocols into first-order Horn clauses on which a dedicated resolution procedure is used to decide equivalence properties. We have shown that our procedure terminates for the class of subterm convergent equational theories. Moreover, the procedure has been implemented in a prototype tool Active Knowledge in Security Protocols and has been effectively tested on examples. Some of the examples were outside the scope of existing tools, including checking anonymity of an electronic voting protocol due to Okamoto.", acknowledgement = ack-nhfb, articleno = "23", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Facchini:2016:IPG, author = "Alessandro Facchini and Filip Murlak and Michal Skrzypczak", title = "Index Problems for Game Automata", journal = j-TOCL, volume = "17", number = "4", pages = "24:1--24:??", month = nov, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2946800", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:14 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "For a given regular language of infinite trees, one can ask about the minimal number of priorities needed to recognize this language with a nondeterministic, alternating, or weak alternating parity automaton. These questions are known as, respectively, the nondeterministic, alternating, and weak Rabin-Mostowski index problems. Whether they can be answered effectively is a long-standing open problem, solved so far only for languages recognizable by deterministic automata (the alternating variant trivializes). We investigate a wider class of regular languages, recognizable by so-called game automata, which can be seen as the closure of deterministic ones under complementation and composition. Game automata are known to recognize languages arbitrarily high in the alternating Rabin-Mostowski index hierarchy; that is, the alternating index problem does not trivialize anymore. Our main contribution is that all three index problems are decidable for languages recognizable by game automata. Additionally, we show that it is decidable whether a given regular language can be recognized by a game automaton.", acknowledgement = ack-nhfb, articleno = "24", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Elberfeld:2016:WFO, author = "Michael Elberfeld and Martin Grohe and Till Tantau", title = "Where First-Order and Monadic Second-Order Logic Coincide", journal = j-TOCL, volume = "17", number = "4", pages = "25:1--25:??", month = nov, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2946799", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:14 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We study on which classes of graphs first-order logic ( fo) and monadic second-order logic (mso) have the same expressive power. We show that for all classes C of graphs that are closed under taking subgraphs, fo and mso have the same expressive power on C if and only if, C has bounded tree depth. Tree depth is a graph invariant that measures the similarity of a graph to a star in a similar way that tree width measures the similarity of a graph to a tree. For classes just closed under taking induced subgraphs, we show an analogous result for guarded second-order logic (gso), the variant of mso that not only allows quantification over vertex sets but also over edge sets. A key tool in our proof is a Feferman--Vaught-type theorem that works for infinite collections of structures despite being constructive.", acknowledgement = ack-nhfb, articleno = "25", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Carlucci:2016:PCP, author = "Lorenzo Carlucci and Nicola Galesi and Massimo Lauria", title = "On the Proof Complexity of {Paris--Harrington} and Off-Diagonal {Ramsey} Tautologies", journal = j-TOCL, volume = "17", number = "4", pages = "26:1--26:??", month = nov, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2946801", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:14 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We study the proof complexity of Paris-Harrington's Large Ramsey Theorem for bi-colorings of graphs and of off-diagonal Ramsey's Theorem. For Paris-Harrington, we prove a non-trivial conditional lower bound in Resolution and a non-trivial upper bound in bounded-depth Frege. The lower bound is conditional on a (very reasonable) hardness assumption for a weak (quasi-polynomial) Pigeonhole principle in R es(2). We show that under such an assumption, there is no refutation of the Paris-Harrington formulas of size quasi-polynomial in the number of propositional variables. The proof technique for the lower bound extends the idea of using a combinatorial principle to blow up a counterexample for another combinatorial principle beyond the threshold of inconsistency. A strong link with the proof complexity of an unbalanced off-diagonal Ramsey principle is established. This is obtained by adapting some constructions due to Erd{\H{o}}s and Mills. We prove a non-trivial Resolution lower bound for a family of such off-diagonal Ramsey principles.", acknowledgement = ack-nhfb, articleno = "26", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Bogaerts:2016:WFS, author = "Bart Bogaerts and Joost Vennekens and Marc Denecker", title = "On Well-Founded Set-Inductions and Locally Monotone Operators", journal = j-TOCL, volume = "17", number = "4", pages = "27:1--27:??", month = nov, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2963096", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:14 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "In the past, compelling arguments in favour of the well-founded semantics for autoepistemic logic have been presented. In this article, we show that for certain classes of theories, this semantics fails to identify the unique intended model. We solve this problem by refining the well-founded semantics. We develop our work in approximation fixpoint theory, an abstract algebraical study of semantics of nonmonotonic logics. As such, our results also apply to logic programming, default logic, Dung's argumentation frameworks, and abstract dialectical frameworks.", acknowledgement = ack-nhfb, articleno = "27", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Furusawa:2016:TM, author = "Hitoshi Furusawa and Georg Struth", title = "Taming Multirelations", journal = j-TOCL, volume = "17", number = "4", pages = "28:1--28:??", month = nov, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2964907", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:14 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Binary multirelations generalise binary relations by associating elements of a set to its subsets. We study the structure and algebra of multirelations under the operations of union, intersection, sequential, and parallel composition, as well as finite and infinite iteration. Starting from a set-theoretic investigation, we propose axiom systems for multirelations in contexts ranging from bi-monoids to bi-quantales.", acknowledgement = ack-nhfb, articleno = "28", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Sojakova:2016:ETP, author = "Kristina Sojakova", title = "The Equivalence of the Torus and the Product of Two Circles in Homotopy Type Theory", journal = j-TOCL, volume = "17", number = "4", pages = "29:1--29:??", month = nov, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2992783", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:14 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Homotopy type theory is a new branch of mathematics that merges insights from abstract homotopy theory and higher category theory with those of logic and type theory. It allows us to represent a variety of mathematical objects as basic type-theoretic construction, higher inductive types. We present a proof that in homotopy type theory, the torus is equivalent to the product of two circles. This result indicates that the synthetic definition of torus as a higher inductive type is indeed correct.", acknowledgement = ack-nhfb, articleno = "29", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Schubert:2016:HHP, author = "Aleksy Schubert and Pawel Urzyczyn and Daria Walukiewicz-Chrzaszcz", title = "How Hard Is Positive Quantification?", journal = j-TOCL, volume = "17", number = "4", pages = "30:1--30:??", month = nov, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2981544", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:14 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We show that the constructive predicate logic with positive (covariant) quantification is hard for doubly exponential universal time, that is, for the class co- 2-N exptime. Our approach is to represent proof-search as computation of an alternating automaton. The memory of the automaton is structured in a way that strictly corresponds to scopes of the binders used in the constructed proof. This provides an application of automata-theoretic techniques in proof theory.", acknowledgement = ack-nhfb, articleno = "30", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Charatonik:2016:TVL, author = "Witold Charatonik and Piotr Witkowski", title = "Two-Variable Logic with Counting and Trees", journal = j-TOCL, volume = "17", number = "4", pages = "31:1--31:??", month = nov, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2983622", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:14 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "We consider the two-variable logic with counting quantifiers (C$^2$ ) interpreted over finite structures that contain two forests of ranked trees. This logic is strictly more expressive than standard C$^2$ and it is no longer a fragment of first-order logic. In particular, it can express that a structure is a ranked tree, a cycle, or a connected graph of bounded degree. It is also strictly more expressive than first-order logic with two variables and two successor relations of two finite linear orders. We present a decision procedure for the satisfiability problem for this logic. The procedure runs in NE xpTime, which is optimal since the satisfiability problem for plain C$^2$ is NExpTime-complete.", acknowledgement = ack-nhfb, articleno = "31", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", } @Article{Benaim:2016:CTV, author = "Saguy Benaim and Michael Benedikt and Witold Charatonik and Emanuel Kiero'nski and Rastislav Lenhardt and Filip Mazowiecki and James Worrell", title = "Complexity of Two-Variable Logic on Finite Trees", journal = j-TOCL, volume = "17", number = "4", pages = "32:1--32:??", month = nov, year = "2016", CODEN = "????", DOI = "https://doi.org/10.1145/2996796", ISSN = "1529-3785 (print), 1557-945X (electronic)", ISSN-L = "1529-3785", bibdate = "Wed Mar 15 16:49:14 MDT 2017", bibsource = "http://www.acm.org/pubs/contents/journals/tocl/; http://www.math.utah.edu/pub/tex/bib/tocl.bib", abstract = "Verification of properties expressed in the two-variable fragment of first-order logic FO$^2$ has been investigated in a number of contexts. The satisfiability problem for FO$^2$ over arbitrary structures is known to be NEXPTIME-complete, with satisfiable formulas having exponential-sized models. Over words, where FO$^2$ is known to have the same expressiveness as unary temporal logic, satisfiability is again NEXPTIME-complete. Over finite labelled ordered trees, FO$^2$ has the same expressiveness as navigational XPath, a popular query language for XML documents. Prior work on XPath and FO$^2$ gives a 2EXPTIME bound for satisfiability of FO$^2$ over trees. This work contains a comprehensive analysis of the complexity of FO$^2$ on trees, and on the size and depth of models. We show that different techniques are required depending on the vocabulary used, whether the trees are ranked or unranked, and the encoding of labels on trees. We also look at a natural restriction of FO$^2$, its guarded version, GF$^2$. Our results depend on an analysis of types in models of FO$^2$ formulas, including techniques for controlling the number of distinct subtrees, the depth, and the size of a witness to satisfiability for FO$^2$ sentences over finite trees.", acknowledgement = ack-nhfb, articleno = "32", fjournal = "ACM Transactions on Computational Logic", journal-URL = "http://portal.acm.org/browse_dl.cfm?idx=J773", }