Semantics of Normal Goals as Acquisitors Caused by Negation as Failure


IEICE TRANSACTIONS on Information and Systems   Vol.E86-D   No.6   pp.993-1000
Publication Date: 2003/06/01
Online ISSN: 
Print ISSN: 0916-8532
Type of Manuscript: PAPER
Category: Theory and Models of Software
logic programming,  model theory,  negation as failure,  

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We are concerned with semantic views on an extended version of SLD resolution with negation as failure (SLDNF resolution) for normal logic programs, which Eshghi and Kowalski (1989) presented by making the SLDNF resolution capable of keeping negated predicates in memory and of extracting abducible predicates. This paper deals with its formal representation in relational form, for the purpose of interpreting the normal goal as an acquisitor of negated predicates stored in memory. Some set acquired by the derivations which the normal goal evokes is defined to be a semantics of the goal, under the constraint that the set is as large as possible and does not violate consistency in model theory. The semantics is discussed with relation to the 3-valued logic model theory, where the model theory is represented by alternating fixpoint semantics (Van Gelder, 1993). For simplicity of treatment, this paper is concerned with the normal logic program in the propositional logic.