Abstract: After undergoing the stages wireframe,surface modeling and solid modeling,a unified product model,which holds a variety of constraints in engineering,supports the design process,and unites the wireframe, surface modeling and solid modeling,is a general tendency of the modeling technology.This paper discusses how to build a unified product model by using the nonmanifold method.The concept of complex in algebraic topology is introduced into the non manifold method,and the non manifold is given a new B REP——Adjunction Edge Structure. Based on it, some basic operators and high level operators are built.In the same time,the model, which has a rigorous mathematical basis,is flexible and easy to extend, and it also holds the lamina face, lamina edge and lamina vertex.As a result,the variety of constraints in engineering,such as parametric constraints,optimization methods,artificial intelligent,etc,can be added to the system.The model may be the kernel of the new generation of CAD system——intelligent CAD system.

Key words: CAD, solid modeling, non-manifold, complex, CW-complex, polyhedron