The Design-Methods Comparison Project

Abstract

Early in the system design process, a design method must be chosen. This choice is usually dictated by what methods the designer has previously used, not by an open selection process. We provide descriptions of some available design methods and examples of their use. We develop benchmark problems that are solved by a variety of design methods and which identify characteristics of problems that might make one system design method more or less appropriate. The question we wish to answer is, “For which type of problem is each method best?” If a system is to be built, then that system must ultimately be described as a collection of state machines. However, these state machines are often not created by the systems engineers. The systems engineers use some method to create a high-level abstraction of the desired system. Then they turn this abstraction over to the specialty engineers who actually reduce it to a collection of state machines. We present solutions for a simple design problem by using the following 11 high-level system design methods: state transition diagrams, algorithmic state machine (ASM) notation, model-based system engineering, graphical description language, RDD-100, structured analysis, functional decomposition, object-oriented analysis (OOA) with Shlaer-Mellor notation, OOA and object-oriented design (OOD) with Booch notation, an operational evaluation modeling-directed graph, and IDEF0. Each method was used by an expert user of that method. The solutions presented make it obvious that the choice of a design method greatly effects the resulting system design