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arXiv 1012.5847cs.AI
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关于逻辑程序的初等循环

On Elementary Loops of Logic Programs

Universität Potsdam(波茨坦大学);Arizona State University(亚利桑那州立大学);University of Kentucky(肯塔基大学)

Martin Gebser, Joohyung Lee, Yuliya Lierler

摘要:

利用初等循环的概念,Gebser和Schaub通过只考虑初等循环的循环公式,改进了Lin和Zhao关于循环公式的定理。在这篇文章中,我们重新制定了他们的基本循环的定义,将其扩展到析取程序,并研究了基本循环的几个性质,包括最大基本循环如何与最小无基集相关。结果提供了有用的见解,稳定的模型语义的基本循环。对于一个非析取程序,使用一个基本循环的图论表征,我们表明,识别一个基本循环的问题是易处理的。另一方面,我们证明了相应的问题是{ \sf coNP}-完全的析取程序。基于基本循环的概念,我们提出了Head-Elementary-Loop-Free(HEF)程序类,它严格地推广了Ben-Eliyahu和Dechter提出的Head-Cycle-Free(HCF)程序类.和HCF程序一样,HEF程序也可以在多项式时间内通过将头原子移入体原子而转化为等价的非析取程序。

英文摘要:

Using the notion of an elementary loop, Gebser and Schaub refined the theorem on loop formulas due to Lin and Zhao by considering loop formulas of elementary loops only. In this article, we reformulate their definition of an elementary loop, extend it to disjunctive programs, and study several properties of elementary loops, including how maximal elementary loops are related to minimal unfounded sets. The results provide useful insights into the stable model semantics in terms of elementary loops. For a nondisjunctive program, using a graph-theoretic characterization of an elementary loop, we show that the problem of recognizing an elementary loop is tractable. On the other hand, we show that the corresponding problem is {\sf coNP}-complete for a disjunctive program. Based on the notion of an elementary loop, we present the class of Head-Elementary-loop-Free (HEF) programs, which strictly generalizes the class of Head-Cycle-Free (HCF) programs due to Ben-Eliyahu and Dechter. Like an HCF program, an HEF program can be turned into an equivalent nondisjunctive program in polynomial time by shifting head atoms into the body.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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