As a design progresses, the design space becomes more constrained due to the decisions that have been made. For example, once a construction material has been chosen, all the properties of that material become constraints that limit and shape future decisions in the design. A constraint model of design will be created that will keep a system of accounts for the designer as a design evolves. The constraint model also includes the idea of appropriate level of detail--that is, the required level of knowledge of properties of a material are different at different points in the design process. A computer model that presents too much information too soon is not useful to the designer. To develop this model, the researchers will study how designers frame the design tasks in different computational environments and how designers work in the different environments of architecture and engineering. As part of the research, a survey and critique of current models and methods for design will be undertaken. One area of emphasis will be the differences and similarities in architectural and engineering design.