Method of equivalent element in parametric CAD

This paper introduces a new method to represent entities and deal with constraints in parametric CAD system. The method is based on equivalent entity, named as method of equivalent element. Using the method, many kinds of complex geometrical elements and constraints could be treated as simple equivalent line(s), so the whole drawing would be translated into its equivalent drawing that is composed of only lines. It can make the parametric work become very regular and efficient.