Engineering design complexity: an investigation of methods and measures

In this paper, two measures are proposed for valuation of size and coupling complexities of design products as abstracted by three distinct representations. The proposed size complexity measure is based on the information theoretic definition of complexity that connects the complexity of a design to the level of entropy, or uncertainty, inherent in the design product. The proposed coupling complexity measure evaluates the decomposability of the graph-based representation of design products. To validate the proposed measures, an experiment is conducted to calculate the complexities of three consumer products based on three product representations, namely, function structure, connectivity graph, and parametric associativity graph. The findings indicate that coupling and size are independent measures of a product's complexity. Thus, it is recommended that both measures should be used. Further, the complexity of a product is not independent of the choice of representation model used to describe the product. This suggests that the complexity of a product will vary with the selected view. Finally, it is shown that the two approaches for measuring complexity of a product are generalizable and can be applied to different representations.