Revised Stable Models - a new semantics for logic programs

This paper introduces an original 2-valued semantics for Normal Logic Programs (NLP), important on its own. Nevertheless, its name draws attention to that it is inspired by and generalizes Stable Model semantics (SM). The definitional distinction consists in the revision of one feature of SM, namely its treatment of odd loops over default negation. This single revised aspect, addressed by means of a Reductio ad Absurdum approach, affords us a fruitful cornucopia of consequences, namely regarding existence, relevance and top-down querying, cumulativity, and implementation. The paper motivates and then defines the Revised Stable Models semantics (rSM), justifying the definition and providing examples. It also presents two rSM semantics preserving program transformations into NLP without odd loops. Properties of rSM are given and contrasted with those of SM. Implementation is examined, and extensions of rSM are given with regard to explicit negation, ‘not’s in heads, and contradiction removal. Conclusions, further work, as well as potential use, terminate the paper.