An autoepistemic logical view of knowledge base

Abstract

Autoepistemic logic (AE) is a non-monotonic logic for modelling beliefs of agents who reflect on their own beliefs. In this paper, we will take such a logical view of knowledge base by treating its contents as its beliefs about a world and its integrity constraints as its beliefs about its contents. We will show how such a view can help us to represent and reason about incomplete knowledge, self-knowledge and negative information. We will also show that an AE logical closure of a knowledge base will neither suffer the inconsistency problem nor the logic-impurity problem that often persist in the standard nonmotonic closures of a kowledge base. In particular, we will show that an AE logic view of integrity constraints provides a finer way of defining integrity constraints than existing definitions. For the logic to be effective, we introduce a a stratified AE proof theory for evaluating queries and maintaining integrity constraints. It is shown that the AE logical view of a stratified knowledge base will yield a unique AE closure of the knowledge base.