Rationality postulates for relevance relations

The paper presents a characterization of relevance as a primitive conceptual notion. Informal definitions for the notions of positive (ir)relevance and negative (ir)relevance are suggested and a set of schemas and rationality postulates for formalizing these notions are proposed. A possible-world approach is adopted to give the relevance-relations a semantics. The semantics is connected to the postulates via a representation theorem. Several conditions for relevance that are derived from the given postulates are inspected. Finally, a method for defining default reasoning in terms of relevance is briefly described