摘要： 本文介绍了在我们研制、开发的一个多用户工程数据库管理系统——MEDAM(Multi-userEngineering DAtabase Management System)中的结构实体以及结构实体中语义约束规则的描述及操作。

Abstract: Information presented in CAD/CAM oriented database for engineering applications is usually too complex to be stored in a single record or in homogeneous sets of records. So, database management systems should include concepts that would deal with this kind of data in a straightforward manner. Therefore, the need arises in the engineering environment to treat complex data structure as single entities. In this paper, the facilities provided by the MEDAMS database management system for viewing and manipulating multiple entities from multiple objects as one entity are described and studied.