Reasoning about Evolving Nonmonotonic Knowledge Bases

Recently, several approaches to updating knowledge bases modeled as extended logic programs (ELPs) have been introduced, ranging from basic methods to incorporate (sequences of) sets of rules into a logic program, to more elaborate methods which use an update policy for specifying how updates must be incorporated. In this paper, we introduce a framework for reasoning about evolving knowledge bases, which are represented as ELPs and maintained by an update policy. We describe a formal model which captures various update approaches, and define a logical language for expressing properties of evolving knowledge bases. We further investigate the semantical properties of knowledge states with respect to reasoning. In particular, we describe finitary characterizations of the evolution, and derive complexity results for our framework.