XSB: A System for Effciently Computing WFS

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Prasad Rao, Konstantinos Sagonas, Terrance Swift, David Scott Warren, Juliana Freire

Published: 1997, Last Modified: 27 Jan 2026LPNMR 1997EveryoneRevisionsBibTeXCC BY-SA 4.0
Abstract: The well-founded model provides a natural and robust semantics for logic programs with negative literals in rule bodies. We implemented the well-founded semantics in the SLG-WAM of XSB [19]. Performance results indicate that the overhead of delay and simplification to Prolog — or tabled — evaluations is minimal. To compute the well-founded semantics, the SLG-WAM adds to an efficient tabling engine for definite programs three operations — negative loop detection, delay and simplification — which serve to detect, to break and to resolve cycles through negation that might arise in evaluating normal programs. XSB is a full Prolog system that closely approximates the ISO standard; additionally, it supports a tight integration of tabled predicates with nontabled predicates.