Introduction

Engineering design is an iterative process, in which the design is continuously modified until it meets the criteria set by the engineers. The traditional design process is carried out by the so called ‘trial and error’ method, in which the designer uses his experience and intuition to lead the design process. This manual based design process has the advantage that the designer’s knowledge can be utilized in the design, and this approach still dominates the design method. But as the design problem becomes more complex, design modification becomes much more difficult. Therefore there is a urgent need for a new tool to guide the design modification.