An engineering design consists of (i) a design analysis where a design candidate is analysed against the expected design criteria and (ii) a design synthesis where a group of potential design candidates are explored, analysed, and compared to find the optimized solution to an engineering problem. An engineering design process begins with the formulation of a design problem. In formulating a design problem, the design needs are interpreted and represented by a set of functional requirements (FRs), and design synthesis is performed to define a set of design parameters (DPs) and a design space for these DP_S. The relational models of DPs and FRs are established in design analysis, and these models are further utilized in design synthesis, so that the design candidates can be compared to optimize the solution to a specified design problem (Bi and Zhang 2001a,b; Bi et al. 2014).