After a decade of research and experimentation, the importance of requirements specification (whatever that means) is generally recognized, and the number of jour-nals and conferences on this subject isgrowing accordingly. 2But results are not yetconsolidated, and practitioners looking for tools and methods available as turnkey systems will be frustrated. This article is an attempt to present some experiences, ideas, and suggestions to those who are interested but may be confused, rather than motivated, by the amount of available material. Many definitions have been suggested for terms like" requirement,"" design,"" specification,"" docu-ment," which are often used in this field. For this article, two simple conventions will be sufficient: A specification is a description of an object, giving its properties of interest; it usually implies that the description should be precise, testable, and formal. 3 A requirement is a property of a product regarded as necessary. 3" Specification" stands for" requirement specification," where suggested by the context.