A major determinant of the quality of software systems is the quality of their requirements, which should be both understandable and precise. Most requirements are written in natural language, good for understandability but lacking in precision. To make requirements precise, researchers have for years advocated the use of mathematics-based notations and methods, known as "formal". Many exist, differing in their style, scope and applicability. The present survey discusses some of the main formal approaches and compares them to informal methods. The analysis uses a set of 9 complementary criteria, such as level of abstraction, tool availability, traceability support. It classifies the approaches into five categories: general-purpose, natural-language, graph/automata, other mathematical notations, seamless (programming-language-based). It presents approaches in all of these categories, altogether 22 different ones, including for example SysML, Relax, Eiffel, Event-B, Alloy. The review discusses a number of open questions, including seamlessness, the role of tools and education, and how to make industrial applications benefit more from the contributions of formal approaches. (This is the full version of the survey, including some sections and two appendices which, because of length restrictions, do not appear in the submitted version.)

中文翻译：

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形式主义在系统需求中的作用（完整版）

软件系统质量的一个主要决定因素是它们的需求质量，它应该是可理解的和精确的。大多数需求是用自然语言编写的，易于理解但缺乏精确性。为了使需求精确，研究人员多年来一直提倡使用基于数学的符号和方法，称为“正式的”。许多存在，其风格、范围和适用性各不相同。本调查讨论了一些主要的正式方法，并将它们与非正式方法进行了比较。该分析使用一组 9 个补充标准，例如抽象级别、工具可用性、可追溯性支持。它将方法分为五类：通用、自然语言、图形/自动机、其他数学符号、无缝（基于编程语言）。它介绍了所有这些类别中的方法，共有 22 种不同的方法，包括例如 SysML、Relax、Eiffel、Event-B、Alloy。该评论讨论了许多开放性问题，包括无缝性、工具和教育的作用，以及如何使工业应用从正式方法的贡献中获益更多。（这是调查的完整版，包括部分章节和两个附录，由于篇幅限制，未在提交的版本中出现。）