Present-day CAD packages play only a small part in the central arena of mechanical engineering design, which involves the synthesis and embodiment of physical components to perform a pre-determined function without unwanted side-effects. The computer cannot properly help the designer in this task until it is able to capture and process the functional requirements of the design. Functional modelling provides a method for achieving this, and raises some challenging geometrical and programming problems. © 1991.
Johnson, A. L. (1991). Designing by functions. Design Studies, 12(1), 51–57. https://doi.org/10.1016/0142-694X(91)90008-K