Abstract: In order to solve the problem of knowledge management and knowledge reuse in the whole lifecycle of products development, a kind of framework of knowledge base of machine product based on ontology is put forward. The similarity is accounted in the four respects of syntax, attribute, structure and instance. So the process of mapping source ontology to object ontology is realized. The product knowledge model is built by using the ontology express language OWL (Web Ontology Language) and the method of case-based reasoning based on ontology is deeply studied too. At last, these methods are applied in the machine products knowledge base subsystem, which belongs to the knowledge management system of manufacturing.

Key words: computer application, knowledge base, ontology, similarity, case-based reasoning