Abstract: To improve the efficiency and accuracy in the process of case retrieval for the product family configuration design, a case retrieval method based on the extension distance is presented. Extension distance contains numeric to numeric, numeric to set and between sets. The difference between the retrieval features is the main standard. Then the extension similarity model is built on the basis of extension distance to meet the configuration demand. And the standard deviation related with the similarity is introduced to distribute the dynamic attribute’s weights which also considers the customer’s preference. A chain saw is used as a case to verify the usefulness and effectiveness. It is demonstrated that the method can process the precise and imprecise information effectively in case retrieval. With VC++6.0 and Solidworks, the configuration system is designed to realize the method mentioned.

Key words: Case-based reasoning, Configuration design, Contradiction problem, Product family, Similarity degree