: In this paper, we propose a fundamental idea of a new CAD architecture to facilitate design knowledge management. This architecture is useful to develop an advanced design support system that encourages a designer to externalize his/her knowledge during a design process and facilitates sharing and reuse of such externalized design knowledge in later stages. We also describe an implementation of this idea called DDMS (Design Documentation Management System). DDMS works as a front-end to KIEF (Knowledge Intensive Engineering Framework) we have been developing. We also illustrate an example of machining tool design to demonstrate the features of DDMS.. Key words: Computer aided design, Knowledge intensive engineering, Knowledge management, Design process, Design document