Semantics of CAD Objects for Generalized Databases

This paper presents some fundamental issues related to the design and implementation of CAD oriented database systems. Integrating databases in sophisticated CAD environments requires functionalities usually not provided by existing systems, e.g relational or entity-relationship systems. For instance, consistency controls have to provide richer and more flexible features than the former "take it or leave it" paradigm. The basic aspects are examined here with respect to the nature of CAD objects, to their consistency states and to their dynamicity. The nature of CAD objects concerns the complexity of their structure and of their relationships. The state of CAD objects concerns their completeness with considerations to their consistency. Finally, the dynamicity of CAD objects concerns the evolving nature of their structure and of their property values, i.e their behavior, with connections to versions and representations. These concepts are defined and detailed with examples drawn from VLSI circuit design. The functionalities of a prototype CAD database system offering new solutions in these areas are presented, calling upon object-oriented concepts and logic-programming. It is currently being tested for VLSI circuit design in cooperation with the CAD Research Dept at CNET.