This paper outlines an approach to the implementation of CAD systems that makes use of a programming paradigm based upon definitions ("definitive programming").
It departs from previous research on "pure definitive notations" - special-purpose notations for interaction - and proposes a general-purpose programming model based upon definitive principles. This model is examined as a possible basis for the development of an integrated framework within which to address the broader issues of a design support environment, including constraint handling and user-interface management. This gives a new perspective on the use of definitive principles for interaction in which the emphasis is upon interpreting a family of definitions as one of many possible "intelligent views" of an interactive system. It also establishes a closer relationship between the definitive programming approach to CAD and the study of CAD from an AI perspective than was previously evident.
The design of an appropriate definitive notation for geometric modelling is a fundamental aspect of the application of definitive principles to CAD software. An appropriate basis for such a notation is presented in an Appendix.