Composition techniques of CAD component model and its implementation

The component models used in CAD are mainly classified into two categories: standard component model and in-house component model.The successful experience should not be copied blindly,although there are some successful instances in both cases.After the analysis of the challenge in development of CAD,the selecting strategy of component model was discussed and an appropriate solution that enhanced some new features and techniques based on standard component model was given.At last,a new composition technique of component reused and extension based on COM was represented and implemented.This technique had two advantageous properties.It didn't change either the identity of the component being extended,or the Code of the component being extended.