应用程序开发期从1970年代初到1980年代中期。

软件定义时期的任务是：确定软件开发工程必须完成的总目标；确定工程的可行性；导出实现工程目标应该采用的策略及系统必须完成的功能；估计完成该项工程需要的资金和成本，并制定工程进度表。这个时期的工作通常又称为系统分析，由系统分析员负责完成 开发时期具体设计和实现在前一时期定义的软件 运行维护的主要任务是使软件持久的满足用户的需要 A Process Framework Process framework Framework activities work tasks work products milestones & deliverables QA checkpoints Umbrella Activities * Framework Activities Communication Planning Modeling Analysis of requirements Design Construction Code generation Testing Deployment * Umbrella Activities Software project management Formal technical reviews Software quality assurance Software configuration management Work product preparation and production Reusability management Measurement Risk management * Adapting a Process Model the overall flow of activities, actions, and tasks and the interdependencies among them the degree to which actions and tasks are defined within each framework activity the degree to which work products are identified and required the manner which quality assurance activities are applied the manner in which project tracking and control activities are applied the overall degree of detail and rigor with which the process is described the degree to which the customer and other stakeholders are involved with the project the level of autonomy given to the software team the degree to which team organization and roles are prescribed * The Essence of Practice Polya suggests: 1. Understand the problem . 2. Plan a solution . 3. Carry out the plan . 4. Examine the result for accuracy . * 瀑布模型也称为线性顺序模型 在20世纪80年代以前，瀑布模型一直是唯一被广泛采用的生命周期模型 1.阶段间具有顺序性和依赖性。 2.推迟实现的观点。 3.每个阶段必须完成规定的文档;每个阶段结束前完成文档审查,及早改正错误。 传统的瀑布模型过于理想化。事实上，人在工作过程中不可能不犯错误。 在设计阶段可能发生规格说明文档中的错误。 而设计上的缺陷或错误可能在实现过程中显现出来。 在综合测试阶段将发现需求分析、设计或编码阶段的许多错误。 瀑布模型有许多优点：可强迫开发人员采用规范的方法（例如，结构化技术）； 严格地规定了每个阶段必须提交的文档；要求每个阶段交出的所有产品都必须经过质量保证小组的仔细验证。瀑布模型的成功在很大程度上是由于它基本上是一种文档驱动的模型。 ? 适合于用户需求明确、完整、无重大变化的软件项目开发。 快速建立起来的可以在计算机上运行的程序，他所能完

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