On Persistent Semantics for Knowledge

Katsuno and Mendelzon suggested eight postulates for characterizing the semantics of update where the principle of minimal change is embedded [Katsuno and Mendelzon, 1991a]. In this paper we propose a new method for knowledge base update based on persistence. We examine the relations between the two di erent update semantics by investigating the satis ability of Katsuno and Mendelzon's update postulates under our persistent update semantics. We show that the persistence-based update operator satis es most of Katsuno and Mendelzon's update postulates and sometimes satis es all of them, from which we can see the essential distinction between the persistent update and the minimality-based update.