AAAI Publications, Sixteenth International Conference on Principles of Knowledge Representation and Reasoning

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Incorporating Relevance in Epistemic States in Belief Revision
James Delgrande, Pavlos Peppas

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 \sigma 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.