Compound data structure for computer aided design; a survey

The aim of Computer Aided Design is to create in the computer a model of the design problem. For example, an electronic circuit may be being designed; the engineer will use an environment consisting of standard circuit parts, with the laws that govern the operation, and will use this environment, together with the constraints on performance, to build a model which is his proposed solution to the design problem. This model may now be tested against the specification and will generally be modified iteratively until the design goal is achieved, in this case a layout with the required characteristics. It may also be that the design problem is being tackled by a team, in which case several users of the design system may wish to access and transform the model, for instance to display views and projections of it, or check on how it interfaces with a parallel project.