The introduction of a new design support system may change the engineering designer's work situation. Therefore, it may not be possible to derive all the functionalities for a design support system from solely empirical studies of manual design work. Alternatively the design support system could be based on a assertion with a theoretical foundation, which then is verified through empirical studies. However, to develop a design support system, there is a need for a balanced theoretical and empirical approach.This paper presents the results from the first steps in the development of a design support system, indicating a proposal for how to balance a theoretical and empirical approach. The result of this research will be utilized in the development of a Designer's Workbench to support the synthesis activity in mechanical design.