Consistency and Transactions in CAD Database

A CAD database will reach a consistent state only at the end of the design process. This paper provides a framework for transforming the CAD database into the final consistent state. "or this purpose we developed a model of a design object. Each design object can be composed of several representations. Some representations are independent of any other representations and some can be derived using other representations. Several versions of each representations can be stored simultaneously in the database. Using this model we derive a set of global consistency rules. The concept of transaction is refined to suit the CAD environment. A mechanism assisting in reaching the global consistency is described. A protocol controlling the concurrent access to the representation versions is given. Finally the consistency manager observing both the consistency and the concurrency protocol is outlined.