Hierarchical Knowledge Representation Based on Approximations

Abstract

It is difficult even for an expert to fully understand the behavior of a complex system. To do so, human beings often try to view such systems at different levels of abstraction based on their functional structure. The way we understand complex systems is thus mostly hierarchical. A method for hierarchical representation of complex system is proposed which enables acquisition and simultaneous utilization of knowledge expressed at multiple levels using different abstractions based on approximations. We can distinguish three stages on the path to automatic generation of a hierarchical knowledge base depending on the degree of automation. In this paper, the results of the first stage are described, including the implemented method as well as the hierarchical knowledge base constructed for digital circuits. The characteristics of this method can be summarized as follows : ・ Multiple domain theories and the relation between descriptions at different levels are used to express many aspects of a complex system. ・ To keep the whole hierarchical knowledge consistent, information about the approximation used in each hierarchy is stored. Without this information, contradictions which are introduced by the use of approximations decrease the functionality of the knowledge base. ・ An EBL-like method is used to support construction of the consistent hierarchical knowledge base complying with the proposed representation method. Also discussed is how the hierarchical knowledge base constructed by this method can be used in problem solving.