The international standard ISO 10303 (STEP) is being extended to permit the exchange of procedurally defined shape models, with additional parameterization and constraint information, between CAD systems. The transfer of parameterized assembly models is an additional objective. Most of the essential new resources have already been published by ISO, and the remainder are well advanced in the standardization process. Because these are new capabilities, at present not quite complete, there are at present no commercial STEP translators making use of them. However, several proof-of-concept trials have been performed or are in progress, using development versions of the STEP documentation. This paper reports in some detail on one of those trials, and comments on the experience gained. The conclusion is that the standardized exchange of CAD models containing 'design intent' information has been successfully demonstrated, but that the development of translators for that purpose is not an easy task. One particular problem area is pinpointed, where further research is needed to find ways of improving the efficiency of such exchanges.

The paper describes the status of work aimed at extending the international standard ISO 10303 (STEP) to permit the exchange of procedurally defined shape models between CAD systems. Such models are specified by the sequence of operations used to construct them rather than by the explicit elements they contain. They have the advantage of being easy to edit in a receiving system, by contrast with the explicit models that can be exchanged using current standards, which prove to be inert after transfer. The use of the proposed methodology in the exchange of realistic procedural shape models of mechanical parts has already been demonstrated, and a brief account is given of some of the tests that have been performed.