Incorporating Relevance in Epistemic States in Belief Revision
James P. Delgrande, Pavlos Peppas · UTS ePRESS (University of Technology Sydney) · 2018
We present an account of relevance in belief revision where, intuitively, one wants to only consider the relevant part of an agent's epistemic state in a revision.We assume that relevance is a domain-specific notion, and that (ir)relevance assertions are given as part of the agent's epistemic state.Such assertions apply in a given context, and are of the form "in the case that formula σ holds, the Y part of the agent's epistemic state is independent of the rest of the epistemic state", where Y is part of the signature of the language.Two approaches are given, one in which (in semantic terms) conditions are placed on a faithful ranking on possible worlds to enforce the (ir)relevance assertions, and a second in which the possible worlds characterising the agent's beliefs may be modified in a revision.These approaches are shown to yield the same resulting belief set.Corresponding postulates and a representation result are given.The overall approach is compared to that of Parikh's for language splitting as well as with multivalued dependencies in relational databases.