Why Are Requirements So Hard To Get Right?

摘要

There are many instances in the history of system developments that illustrate how difficult it is to discover and understand system requirements in the same way that stakeholders understand them. This has resulted in cancellation of some programs, and has resulted in cost and schedule overruns on other programs. Misunderstanding of requirements is an acute problem in the development of systems for government agencies, but it appears in commercial developments, too, where it takes the form of products that fail to meet market expectations (the Ford Edsel is a classic example). This paper examines the deep reasons why requirements expressed in language are so hard to convey from a stakeholder to a supplier or from consumers to manufacturers. Semiotic concepts are summarized and bolstered with physiological and psychological evidence about the phonemic, syntactic and semantic properties of language. The paper concludes that language is profoundly arbitrary, whether spoken or written, whether in words or in pictures. It is therefore incumbent on all of us to remember the strong principle of communication: each party to a communication must work hard to understand what the other is trying to say. Such effort is one main thing that will help understand requirements. Additional help comes from development methodologies that quickly lower the level of abstraction by demonstrating solutions as early as possible, and by requesting feedback from stakeholders. Automated tools can also help.