A framework for prioritized reasoning based on the choice evaluation

This work addresses the issue of prioritized reasoning in the context of logic programming. The case of preference conditions involving atoms is considered and a refinement of the comparison method of the Answer Set Optimization semantics [4] is presented. The paper introduces the concept of choice, as a set of preference rules describing common choice options in different contexts. Thus, intuitively, in the proposed approach the preference rules are not evaluated separately; but the subset of rules, related to the same choice are individuated and the choice instead of rule satisfaction is considered. The role of constraints in the feasibility of choice options is then investigated and an alternative semantics, evaluating choices on the basis of their really possible (allowed) options, is developed. Complexity analysis is also performed showing that the introduction of choices does not increase the complexity of computing preferred stable models. Copyright 2007 ACM.