Affiliation:
1. University of Ferrara, Ferrara, Italy
2. Coherent Knowledge Systems, Inc. and NOVALincs, Universidade Nova de Lisboa, Portugal
Abstract
As evaluation methods for logic programs have become more sophisticated, the classes of programs for which termination can be guaranteed have expanded. From the perspective of ar set programs that include function symbols, recent work has identified classes for which grounding routines can terminate either on the entire program [Calimeri et al. 2008] or on suitable queries [Baselice et al. 2009]. From the perspective of tabling, it has long been known that a tabling technique called
subgoal abstraction
provides good termination properties for definite programs [Tamaki and Sato 1986], and this result was recently extended to stratified programs via the class of bounded term-size programs [Riguzzi and Swift 2013]. In this article, we provide a formal definition of tabling with subgoal abstraction resulting in the SLG
SA
algorithm. Moreover, we discuss a declarative characterization of the queries and programs for which SLG
SA
terminates. We call this class
strongly bounded term-size programs
and show its equivalence to programs with finite well-founded models. For normal programs, strongly bounded term-size programs strictly includes the finitely ground programs of Calimeri et al. [2008]. SLG
SA
has an asymptotic complexity on strongly bounded term-size programs equal to the best known and produces a residual program that can be sent to an answer set programming system. Finally, we describe the implementation of subgoal abstraction within the SLG-WAM of XSB and provide performance results.
Funder
Fundação para a Ciência e a Tecnologia
Publisher
Association for Computing Machinery (ACM)
Subject
Computational Mathematics,Logic,General Computer Science,Theoretical Computer Science
Cited by
3 articles.
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