In redesign and design for customization, products are changed. During this process a change to one part of the product will, in most cases, result in changes to other parts. The prediction of such change provides a significant challenge in the management of redesign and customization of complex products where many change propagation paths may be possible. This paper reports on an analysis of change behavior based on a case study in Westland Helicopters of rotorcraft design; the development of mathematical models to predict the risk of change propagation in terms of likelihood and impact of change; and the development of a prototype computer support tool to calculate such information for a specific product. With knowledge of likely change propagation paths and their impact on the delivery of the product, design effort can be directed towards avoiding change to “expensive” sub-systems and, where possible, allowing change where it is easier to implement while still achieving the overall changes required.

This paper introduces a new technique called species conservation for evolving paral-lel subpopulations. The technique is based on the concept of dividing the population into several species according to their similarity. Each of these species is built around a dominating individual called the species seed. Species seeds found in the current gen-eration are saved (conserved) by moving them into the next generation. Our technique has proved to be very effective in finding multiple solutions of multimodal optimiza-tion problems. We demonstrate this by applying it to a set of test problems, including some problems known to be deceptive to genetic algorithms.