Meta-level strategies for reformulation of evaluation function during iterative design

Several stages of the design process call for evaluation and comparison of alternatives. The evaluation function embedded in Design Support Systems often remains static throughout the iterative process, remaining identical to that first defined during the initial formulation stage. This results in a loss of accuracy in determining appropriate trade-offs with each successive design iteration. This paper represents a systematic method for re-defining the terms of the evaluation function, depending on the design stage and the alternatives under consideration. Three components are re-defined: the objectives to be included, the range over which trade-offs are negotiable, and the designer's willingness to make those trade-offs. An example of bicycle fork design illustrates the method through four iterations, including material selection and weight versus stiffness trade-offs. Two different customers are considered: racers and average riders. Results indicate different solutions for each type of customer.