| Although many computer-aided design (CAD) systems have been developed and employed for engineering design and manufacturing, these systems are primarily used for modeling the final geometric design results. Modeling of the non-geometric information and the design evolution from conceptual design to detailed design has not been well studied. A design database representation and evolution model is introduced in this thesis for the development of future CAD systems.;In this model, design database is represented at three different levels: meta-class level, class level, and instance level. The concepts and behaviors of different design database modeling components, including entities, properties, relationships, tasks, and specifications, are defined at the meta-class level. The class level design descriptions form the generic design libraries. The design descriptions at the instance level model the specific design cases. Both the geometric descriptions and the non-geometric descriptions are defined and integrated in this model.;The evolution of design database in this model is described by a graph of worlds. Each world models the design descriptions created at a certain design stage. A design is conducted through an evolutionary process from the world with original design requirements to the world with final design results. Among worlds, one is selected as the active world for design database modeling. In a world, only the differences with its preceding world are recorded. Multiple succeeding worlds, representing different design alternatives, can be evolved from the same world. When design descriptions in a preceding world are changed, these changes are propagated to its succeeding worlds automatically.;A prototype design database representation and evolution modeling system has been developed. Case studies have also been conducted to show the effectiveness of the design database representation and evolution modeling approach. |
