Preferences And Nonmonotonic Reasoning

We give an overview of the multifaceted relationship between nonmonotonic logics cold preferences. We discuss how the nonmonotonicity of reasoning itself is closely tied to preferences reasoners have on models of the world or, as we often say here, possible belief sets. Selecting extended logic programming with answer-set semantics as a generic nonmonotonic logic, we show how that logic defines preferred belief sets and how preferred belief sets allow Us to represent and interpret normative statements. Conflicts among program rules (more generally, defaults) give rise to alternative preferred belief sets. We discuss how such conflicts call be resolved based oil implicit specificity or oil explicit rankings of defaults. Finally, we comment on formalisms that explicitly represent preferences oil properties of belief sets. Such formalisms either build preference information directly into rules and modify, the semantics of the logic appropriately or specify preferences oil belief sets independently of the mechanism to define them.