Optimal Models of Disjunctive Logic Programs

Almost all semantics for logic programs with negation identify a set, SEM (P), of models of program P, as the intended semantics of P, and any model M in this class is considered a possible meaning of P w.r.t. the semantics the user has in mind. Thus, for example, in the case of stable models [6], choice mod-els [24], answer sets [7], etc., different possible models correspond to different ways of “completing ” the incomplete information in the logic program. However, different end-users may have different ideas on which of these different models in SEM (P) is a reasonable one from their point of view. For instance, given SEM (P), user U 1 may prefer model