Abstract: In a computer prototyping system, a design is identified from a collection of alternative designs, the identified design best satisfying a set of conceptual level design specifications. One of these alternative designs is selected and their characteristic optimized based on the conceptual level design specifications. The specifications are modified interactively using graphical interfaces for re-evaluating and re-optimizing the designs. Simulation of functional as well as geometrical properties of the design and its components are effected on a computer using graphical design browsers. The performance is analyzed against a set of design specification and the user is allowed to interactively redesign by selecting one of the previous design operations through the graphical interfaces.