Abstract not found

We introduce global SLS-resolution, a procedural semantics for well-founded negation as defined by Van Gelder, Ross and Schlipf. Global SLS-resolution extends Przymusinski 's SLS-resolution, and may be applied to all programs, whether locally stratified or not. 1 Global SLS-resolution is defined in terms of global trees, a new data structure representing the dependence of goals on derived negative subgoals. We prove that global SLS-resolution is sound with respect to the well-founded semantics, and complete for non-floundering queries. While not effective in general, global SLS-resolution is effective for classes of "acyclic" programs, and can be augmented with a memoing device to be effective for all function-free programs. This research was supported by the National Science Foundation under grant IRI-87-22886, by a grant from IBM Corporation, and by the United States Air Force Office of Scientific Research under contract AFOSR-88-0266. A preliminary version of this paper was presen...

The well-founded semantics for "normal" logic programs is described using the alternating fixpoint construction as the basis. The presentation is informal. The semantics is motivated and illustrated through examples, and is compared briefly with earlier semantics for negation. Extensions to other forms of logic program are mentioned briefly. Recent work on practical implementations and applications is surveyed.