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论述了图形库设计的思想和策略，通过水工闸门启闭机图形的分解，提出了一个普遍适用的机械产品图形的组成模型，并成功地用这种模型指导了水工闸门启闭机Ｅ－Ｒ模型（ＥｎｔｉｔｙＲｃｌａｔｉｏｎｓｈｉｐＭｏｄｅｌ）的设计及由Ｅ－Ｒ模型映射成数据模型的设计，成功地将通用关系数据库管理系统改造成工程数据库管理系统．
The idea and strategy of graphic library design are discussed. Based on the decomposition of the graphic of hydraulic gate hoist, a universal compositional model of mechanical product graphic is proposed. The model is used to guide the hydraulic gate hoist E -R model (EntityRclationshipModel) design and mapping from the E-R model into a data model design, the successful transformation of the general relational database management system into a project database management system.