Interest in product data exchange and interfaces in the CAD/CAM area is steadi ly growing. The rapidly increasing graphics applications in engineering and sci ence has led to a great variety of heterogeneous hardware and software products. This has become a major obstacle in the progress of systems integration. To improve this situation CAD/CAM users have called for specification and imple mentation of standardized product data interfaces. These needs resulted in the definition of preliminary standards in this area. Since 1975 activities have been concentrated on developing standards for...