Abstract: In this paper, we propose the notion of knowledge management in engineering database systems, and divide the knowledge based on the symbol object model into three classes: the management of engineering strategies, the one of access control and the one of rules. We put emphasis on the discussion of the reasoning of complex objects, and build the mapping from symbol object model to higher-order logic and then from higher-order logic to first-order one. The reasoning system supports the notions of object identity, type inheritance and semantic relationships, the treatment of sets and of local inconsistent data. Therefore, it is able to meet the needs of a wide variety of engineering applications.