Knowledge-Base Reconstruction by Means of Changing the Viewpoint of Exceptions within Incomplete Knowledge

Abstract

This paper presents a method of knowledge-base reconstruction (KBR) by means of changing the viewpoint of exceptions within the knowledge. The viewpoint means how the exceptions of a class should be decided when we represent the general property of the class by incomplete knowledge which allows exceptions. If there are multiple viewpoints, the different incomplete knowledge is considered according to the viewpoint, and each of them has the different exceptions. Therefore the change of the viewpoint enables us to change both the quantity of the exceptions and the quantity of the rules which are related with these exceptions. By focusing on the viewpoint to reduce these rules, we can make a compact knowledge-base (KB). We realize this KBR by six primary operations classified into the following three types: 1) specialization and generalization of an incomplete rule which represents the incomplete knowledge, 2) addition and deletion of an incomplete rule, and 3) changing the property of a rule. Since the KB must describe the same world before and after this KBR, it should be guaranteed that the application of these operations does not change any conclusions derived from the KB. After proving the intangibility of the conclusions, we propose an algorithm for changing the viewpoint of exceptions.