Computing of p-Stable Models Based on Semi-Negative Normal Programs with Constraints

Currently non-monotonic reasoning (NMR) is a promising approach to model features of common sense reasoning. In order to formalize NMR the research community has applied monotonic logics. The present paper furthers the study of one of the semantics useful in this formalization called p-stable. We introduce three different formats for normal programs with constraints: negative normal programs, restricted negative normal programs and semi-negative normal programs. These forms help to simplify the search of p-stable models of the original program. One of the main results of this paper indicates that the p-stable semantics for semi-negative normal programs with constraints agrees with the Comp semantics. In this way all the applications based on the Comp semantics of semi-negative programs can also be based on p-stable semantics of this type of programs. It is worth to mention that this class of programs can express interesting problems as the 3-coloring problem.