3 - Specifying Requirements

Abstract

One of the most important things that engineers must do is to specify requirements on systems. This is a crucial step in any high-reliability process but, unfortunately, it is often poorly executed. Few engineers have been trained in the capture and management of requirements, and this lack results in huge “Victorian novel” style requirements documents being constructed, which are incomplete, inconsistent and ambiguous. Because such documents are captured in text, they inherently lack the precision necessary for validating them prior to initiating design. This means that the quality of the requirements cannot be assessed in any reliable way. Requirements defects are one of the most important kinds of strategic flaws in systems and are certainly the most expensive to repair because they are introduced early, identified late, and have far-reaching implication and scope. The Unified Modeling Language (UML) and the Harmony process offer a better way. This chapter provides a set of exercises that give practice and experience representing requirements, from both the operational and specification point of view.