On the semantics of logic programs with preferences This work is a contribution to prioritized reasoning in logic programming in the presence of preference relations involving atoms. The technique, providing a new interpretation for prioritized logic programs, is inspired by the semantics of Prioritized Logic Programming and enriched with the use of structural information of preference of Answer Set Optimization Programming. Specifically, the analysis of the logic program is carried out together with the analysis of preferences in order to determine the choice order and the sets of comparable models. The new semantics is compared with other approaches known in the literature and complexity analysis is also performed, showing that, with respect to other similar approaches previously proposed, the complexity of computing preferred stable models does not increase.

On nonmonotonic strategic reasoning Abstract   Strongxcex94Rationalizability introduces firstorder belief restrictions in the analysis of forward induction reasoning. Without actual restrictions, it coincides with Strong Rationalizability (Battigalli 2003, Battigalli and Siniscalchi 2003). These solution concepts are based on the notion of strong belief (Battigalli and Siniscalchi 2002). The nonmonotonicity of strong belief implies that the predictions of Strongxcex94Rationalizability can be inconsistent with Strong Rationalizability. I show that Strongxcex94Rationalizability refines Strong Rationalizability in terms of outcomes when the restrictions correspond to belief in a distribution over terminal nodes. Moreover, under such restrictions, the epistemic priority between rationality and belief restrictions is irrelevant for the predicted outcomes.