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EXPTIME tableaux for ALC
 ARTIFICIAL INTELLIGENCE
, 2000
"... The last years have seen two major advances in Knowledge Representation and Reasoning. First, many interesting problems (ranging from Semistructured Data to Linguistics) were shown to be expressible in logics whose main deductive problems are EXPTIMEcomplete. Second, experiments in automated reaso ..."
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Cited by 58 (4 self)
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The last years have seen two major advances in Knowledge Representation and Reasoning. First, many interesting problems (ranging from Semistructured Data to Linguistics) were shown to be expressible in logics whose main deductive problems are EXPTIMEcomplete. Second, experiments in automated reasoning have substantially broadened the meaning of “practical tractability”. Instances of realistic size for PSPACEcomplete problems are now within reach for implemented systems. Still, there is a gap between the reasoning services needed by the expressive logics mentioned above and those provided by the current systems. Indeed, the algorithms based on treeautomata, which are used to prove EXPTIMEcompleteness, require exponential time and space even in simple cases. On the other hand, current algorithms based on tableau methods can take advantage of such cases, but require double exponential time in the worst case. We propose a tableau calculus for the description logic ALC for checking the satisfiability of a concept with respect to a TBox with general axioms, and transform it into the first simple tableaubased decision procedure working in single exponential time. To guarantee the ease of implementation, we also discuss the effects that optimizations (propositional backjumping, simplification, semantic branching, etc.) might have on our complexity result, and introduce a few optimizations ourselves.
Single step tableaux for modal logics: Computational properties, complexity and methodology
 Journal of Automated Reasoning
"... Abstract. Single Step Tableaux (SST) are the basis of a calculus for modal logics that combines different features of sequent and prefixed tableaux into a simple, modular, strongly analytic, and effective calculus for a wide range of modal logics. The paper presents a number of the computational res ..."
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Cited by 5 (0 self)
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Abstract. Single Step Tableaux (SST) are the basis of a calculus for modal logics that combines different features of sequent and prefixed tableaux into a simple, modular, strongly analytic, and effective calculus for a wide range of modal logics. The paper presents a number of the computational results about SST (confluence, decidability, space complexity, modularity, etc.) and compares SST with other formalisms such as translation methods, modal resolution, and Gentzentype tableaux. For instance, it discusses the feasibility and infeasibility of deriving decision procedures for SST and translationbased methods by replacing loop checking techniques with simpler termination checks. The complexity of searching for validity and logical consequence with SST and other methods is discussed. Minimal conditions on SST search strategies are proven to yield PSPACE (and NPTIME for S5 and KD45) decision procedures. The paper also presents the methodology underlying the construction of the correctness and completeness proofs. Key words: modal logics, prefixed tableaux, confluence, complexity, decision procedures, direct and translation methods.
INTEGRATION OF DECISION PROCEDURES INTO HIGHORDER INTERACTIVE PROVERS
, 2006
"... An efficient proof assistant uses a wide range of decision procedures, including automatic verification of validity of arithmetical formulas with linear terms. Since the final product of a proof assistant is a formalized and verified proof, it prompts an additional task of building proofs of formula ..."
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Cited by 2 (0 self)
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An efficient proof assistant uses a wide range of decision procedures, including automatic verification of validity of arithmetical formulas with linear terms. Since the final product of a proof assistant is a formalized and verified proof, it prompts an additional task of building proofs of formulas, which validity is established by such a decision procedure. We present an implementation of several decision procedures for arithmetical formulas with linear terms in the MetaPRL proof assistant in a way that provides formal proofs of formulas found valid by those procedures. We also present an implementation of a theorem prover for the logic of justified common knowledge S4 J n introduced in [Artemov, 2004]. This system captures the notion of justified common knowledge, which is free of some of the deficiencies of the usual common knowledge operator, and is yet sufficient for the analysis of epistemic problems where common knowledge has been traditionally applied. In particular, S4 J n enjoys cutelimination, which introduces the possibility of automatic proof search in the logic of common