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Automated Verification of Weak Equivalence within the smodels System*

Published online by Cambridge University Press:  01 November 2007

TOMI JANHUNEN  and
EMILIA OIKARINEN
TOMI JANHUNEN
Affiliation:
Helsinki University of Technology, Department of Computer Science and Engineering, Laboratory for Theoretical Computer Science, P.O. Box 5400, FI-02015 TKK, Finland (e-mail: [email protected], [email protected])
EMILIA OIKARINEN
Affiliation:
Helsinki University of Technology, Department of Computer Science and Engineering, Laboratory for Theoretical Computer Science, P.O. Box 5400, FI-02015 TKK, Finland (e-mail: [email protected], [email protected])
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Abstract

In answer set programming (ASP), a problem at hand is solved by (i) writing a logic program whose answer sets correspond to the solutions of the problem, and by (ii) computing the answer sets of the program using an answer set solver as a search engine. Typically, a programmer creates a series of gradually improving logic programs for a particular problem when optimizing program length and execution time on a particular solver. This leads the programmer to a meta-level problem of ensuring that the programs are equivalent, i.e., they give rise to the same answer sets. To ease answer set programming at methodological level, we propose a translation-based method for verifying the equivalence of logic programs. The basic idea is to translate logic programs P and Q under consideration into a single logic program EQT(P,Q) whose answer sets (if such exist) yield counter-examples to the equivalence of P and Q. The method is developed here in a slightly more general setting by taking the visibility of atoms properly into account when comparing answer sets. The translation-based approach presented in the paper has been implemented as a translator called lpeq that enables the verification of weak equivalence within the smodels system using the same search engine as for the search of models. Our experiments with lpeq and smodels suggest that establishing the equivalence of logic programs in this way is in certain cases much faster than naive cross-checking of answer sets.

Keywords

Answer set programmingweak equivalenceprogramming methodologyprogram optimization
Type
Regular Papers
Information
Theory and Practice of Logic Programming , Volume 7 , Issue 6 , November 2007 , pp. 697 - 744
Copyright
Copyright © Cambridge University Press 2007

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