2 research outputs found
Terminating Evaluation of Logic Programs with Finite Three-Valued Models
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 answer 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 paper
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 wellfounded 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 termsize 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