摘要
本文根据工程图中开式约束网络构成主要几何约束结构这一事实，通过引入尺寸树的概念，从而将几何约束系统用树的结构来描述。通过对基于约束的图形块的处理，实现Ａｕｔｏ－ＣＡＤ图形块的参数化。
Based upon the fact that the open constraint network constitutes the principal geometric constraint structure in engineering drawings,the geometric constraint system can be expressed by the dimension tree.The AutoCAD parametric block function is realized by dealing with the drawing blocks based on the geometric constraint.
