A rational design process: How and why to fake it

Software Engineers have been searching for the ideal software development process: a process in which programs are derived from specifications in the same way that lemmas and theorems are derived from axioms in published proofs. After explaining why we can never achieve it, this paper describes such a process. The process is described in terms of a sequence of documents that should be produced on the way to producing the software. We show that such documents can serve several purposes. They provide a basis for preliminary design review, serve as reference material during the coding, and guide the maintenance programmer in his work. We discuss how these documents can be constructed using the same principles that should guide the software design. The resulting documentation is worth much more than the "afterthought" documentation that is usually produced. If we take the care to keep all of the documents up-to-date, we can create the appearance of a fully rational design process.