REPRESENTING THE ENGINEERING DESIGN PROCESS - 2 HYPOTHESES

A representation of the design process is proposed that is based on the exploration model of Smithers et al. Although it was developed round the characteristics of the chemical-plant design area, the author believes that it is applicable to any other area, as long as spatial reasoning is not involved. The representation supports the exploration of the different alternatives generated by the use of aggregation and refinement operators, the consideration of different operating values, and all the combinations of the above. Apart from being able to explore a network of alternatives and expand any node at any point in time, a designer can propagate changes to the design in any selected direction. The representation depends on two hypotheses: (a) the decomposition-of-information hypothesis, and (b) the identical-object hypothesis. Both have been used in the past for different purposes, and the results presented in the paper indicate that they are sound. A COMMON LISP object-oriented system is used for the representation of the object to be designed (a chemical plant). An assumption-based truth maintenance system is used to record the dependencies of the equipment and alternative plants, and to support the exploration of the design space.