FLP answer set semantics without circular justifications for general logic programs

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	FLP answer set semantics without circular justifications for general logic programs
	Shen, Yi-Dong (1) ; Wang, Kewen (2) ; Eiter, Thomas (3) ; Fink, Michael (3) ; Redl, Christoph (3) ; Krennwallner, Thomas (3) ; Deng, Jun (1)
刊名	Artificial Intelligence
	2014
卷号	213 页码:1-41
关键词	Answer set programming Knowledge representation Nonmonotonic reasoning Logic programs with first-order formulas Level mappings Circular justifications
ISSN号	43702
通讯作者	Shen, Y.-D.(ydshen@ios.ac.cn)
中文摘要	The answer set semantics presented by Faber et al. [27] has been widely used to define so called FLP answer sets for different types of logic programs. However, it was recently observed that when being extended from normal to more general classes of logic programs, this approach may produce answer sets with circular justifications that are caused by self-supporting loops. The main reason for this behavior is that the FLP answer set semantics is not fully constructive by a bottom up construction of answer sets. In this paper, we overcome this problem by enhancing the FLP answer set semantics with a level mapping formalism such that every answer set I can be built by fixpoint iteration of a one-step provability operator (more precisely, an extended van Emden-Kowalski operator for the FLP reduct f^ΠI). This is inspired by the fact that under the standard answer set semantics, each answer set I of a normal logic program Π is obtainable by fixpoint iteration of the standard van Emden-Kowalski one-step provability operator for the Gelfond-Lifschitz reduct ^ΠI, which induces a level mapping. The enhanced FLP answer sets, which we call well-justified FLP answer sets, are thanks to the level mapping free of circular justifications. As a general framework, the well-justified FLP answer set semantics applies to logic programs with first-order formulas, logic programs with aggregates, description logic programs, hex-programs etc., provided that the rule satisfaction is properly extended to such general logic programs. We study in depth the computational complexity of FLP and well-justified FLP answer sets for general classes of logic programs. Our results show that the level mapping does not increase the worst-case complexity of FLP answer sets. Furthermore, we describe an implementation of the well-justified FLP answer set semantics, and report about an experimental evaluation, which indicates a potential for performance improvements by the level mapping in practice. © 2014 The Authors.
英文摘要	The answer set semantics presented by Faber et al. [27] has been widely used to define so called FLP answer sets for different types of logic programs. However, it was recently observed that when being extended from normal to more general classes of logic programs, this approach may produce answer sets with circular justifications that are caused by self-supporting loops. The main reason for this behavior is that the FLP answer set semantics is not fully constructive by a bottom up construction of answer sets. In this paper, we overcome this problem by enhancing the FLP answer set semantics with a level mapping formalism such that every answer set I can be built by fixpoint iteration of a one-step provability operator (more precisely, an extended van Emden-Kowalski operator for the FLP reduct f^ΠI). This is inspired by the fact that under the standard answer set semantics, each answer set I of a normal logic program Π is obtainable by fixpoint iteration of the standard van Emden-Kowalski one-step provability operator for the Gelfond-Lifschitz reduct ^ΠI, which induces a level mapping. The enhanced FLP answer sets, which we call well-justified FLP answer sets, are thanks to the level mapping free of circular justifications. As a general framework, the well-justified FLP answer set semantics applies to logic programs with first-order formulas, logic programs with aggregates, description logic programs, hex-programs etc., provided that the rule satisfaction is properly extended to such general logic programs. We study in depth the computational complexity of FLP and well-justified FLP answer sets for general classes of logic programs. Our results show that the level mapping does not increase the worst-case complexity of FLP answer sets. Furthermore, we describe an implementation of the well-justified FLP answer set semantics, and report about an experimental evaluation, which indicates a potential for performance improvements by the level mapping in practice. © 2014 The Authors.
收录类别	SCI ; EI
语种	英语
WOS记录号	WOS:000337772500001
公开日期	2014-12-16
内容类型	期刊论文
源URL	[http://ir.iscas.ac.cn/handle/311060/16844]
专题	软件研究所_软件所图书馆_期刊论文
推荐引用方式 GB/T 7714	Shen, Yi-Dong ,Wang, Kewen ,Eiter, Thomas ,et al. FLP answer set semantics without circular justifications for general logic programs[J]. Artificial Intelligence,2014,213:1-41.
APA	Shen, Yi-Dong .,Wang, Kewen .,Eiter, Thomas .,Fink, Michael .,Redl, Christoph .,...&Deng, Jun .(2014).FLP answer set semantics without circular justifications for general logic programs.Artificial Intelligence,213,1-41.
MLA	Shen, Yi-Dong ,et al."FLP answer set semantics without circular justifications for general logic programs".Artificial Intelligence 213(2014):1-41.