“软件工程”教学课件05软件需求分析.ppt

Essential and Implementation Views An essential view of software requirements presents the functions to be accomplished and information to be process without regard to implementation. The implementation view of software require-ments presents the real world manifestation of processing functions and information structures. In some cases,a physical representation is developed as the first step in software design. The Software Requirements Specification 软件计划 系统定义 需求分析 商业需要 其他系统元素（硬件等）的功能 代价、资源、进度 软件功能 软件作用范围 软件需求规格说明书 The Software Requirements Specification 最好全部由用户/需求者编写，但实际上都由开发者和用户/需求者共同编写。 该说明书是分析和综合结果的描述，包括软件功能、性能、接口、有效性和逻辑模型的描述 软件需求规格说明书的描述方法： 自然语言 格式化语言 形式化语言 The Software Requirements Specification （SRS outline） Introduction Information description Functional description Behavioral description Validation criteria Bibliography Appendix 编写初步用户使用手册和确认测试计划 The Software Requirements Specification 正确性 无二义性 完整性 一致性 非计算机人员可以理解 可修改性 可跟踪性 Specification Review 复审：该阶段完成标志（由用户/需求者，管理部门，开发人员共同承担） Review of a software requirements specifica-tion(and/or prototype) is conducted by both software developer and customer.Because the specification forms the foundation for design and subsequent software engineering activities,extreme care should be taken in conducting the review. Specification Review 采用需求确认检查单进行需求评审 正式技术评审 验证软件需求的原则 作为需求分析阶段工作的复查手段，应该对功能的正确性、完整性和清晰性以及其他需求给予评价。 一致性：所有的需求是一致的，没有任何矛盾。 完整性：需求必须是完整的，没有任何功能和性能的遗漏。 现实性：完成需求所要求的软件和硬件条件，目前是可以达到的。 有效性：需求是有效的，可以解决用户的问题 。 Summary Analysis must focus on the information, functional,and behavioral domains of a problem.To better understand what is required,models are created, the problem is partitioned,and representations that depict the essence of requirements and later, implementation detail,are developed. Summary In many cases,it is not possible to completely specify a problem at an early stage.Prototyping offers an alternative approach that results in an executable model of software from which requirements can be refined. 开发原型系