摘要： 工程数据包含图形信息与文字数值属性信息。为了描述工程数据,本文采用了分层描述的思想,即将具有多个部件的子图抽象为一个概形图,用于上层子图的描述。它易于描述、便于理解、大大减少了存贮量。本文分析了他们共同的特点,指出只要设计好部件分布关系、关键点分布关系、线段分布关系以及子图的动态定义,就可以精确地描述子图的结构及其属性。并扩充关系代数的功能,提出一种适于工程数据描述的数据子语言,并以实例说明其使用方法。

Abstract: Engineering data include figure information and alphanumeric attribute information, the method of hierarchical description is used to describe engineering data, and reduces the parts of the low layer sub-figure to one general-figure in high layer sub-figure, thus making the engineering figure easy to describe and understand and memory space reduced. In order to describe physical sub-engineering figure, the common features of these figures are analysed. If the distributive relations of parts, lines and key points and dynamical definition of sub-figures are designed well, the structure and attribution of sub-figures will be descri bed exactly. The engineering data demands relational algebraic function be expanded so that the figure information can be handled. Finally examples are illustrated.