On Propositional Knowledge Base Updates

It is well known that the minimal change principle was widely used in propositional knowledge base updates. However, recent research has shown that under some circumstances, the conventional minimal change methods were inappropriate for updating knowledge bases with disjunctive eeects. In this paper we propose a new method for the knowledge base update based on a persistence principle, which provides conservative results for updating knowledge bases with implicit and disjunc-tive eeects. As it will be shown, our approach avoids the diiculty with the minimal change principle and can be also extended to derive preferred update solutions if more domain information is provided. To characterize properties of the persistence-based update method, we investigate the relationship between the minimal change update semantics and persistent update semantics in detail.