Disjunctive Update, Minimal Change, and Default Reasoning

It is well known that the minimal change principle was widely used in knowledge base updates. However, recent research has shown that conventional minimal change methods, eg. the PMA 9], are generally problematic for updating knowledge bases with disjunctive information under some circumstances. In this paper, we propose a new approach, which is called the minimal change with exceptions (the MCE), to deal with this problem in propositional knowledge base updates. We show that the MCE generalizes the PMA and still satisses the standard Katsuno and Mendelzon's update postulates. Furthermore, we also investigate the relationship between update and default reasoning. In particular, we represent a translation from the MCE to extended disjunctive default theories and prove the soundness and completeness of such translation relative to the semantics of the MCE.