Head-Elementary-Set-Free Logic Programs

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Head-Elementary-Set-Free Logic Programs
Abstract. The recently proposed notion of an elementary set yielded a refinement of the theorem on loop formulas, telling us that the stable models of a disjunctive logic program can be characterized by the loop formulas of its elementary sets. Based on the notion of an elementary set, we propose the notion of head-elementary-set-free (HEF) programs, a more general class of disjunctive programs than head-cycle-free (HCF) programs proposed by Ben-Eliyahu and Dechter, that can still be turned into nondisjunctive programs in polynomial time and space by ”shifting” the head atoms into the body. We show several properties of HEF programs that generalize earlier results on HCF programs. Given an HEF program, we provide an algorithm for finding an elementary set whose loop formula is not satisfied, which has a potential for improving stable model computation by answer set solvers.
Martin Gebser, Joohyung Lee, Yuliya Lierler
Added 08 Jun 2010
Updated 08 Jun 2010
Type Conference
Year 2007
Authors Martin Gebser, Joohyung Lee, Yuliya Lierler
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