Process Models

• Process model is a policy and guide, it is a description of the development process.

• Waterfall model

  • classic: 只有正向箭头

  • feedback waterfall model: 有反馈，但是只反馈给上一级

  • 

  • 特点：清楚的分工，一致性和好的文档

  • 应用：参与复杂合同项目的多家公司

  • 缺点：

    • difficult to respond to changing requirements

    • Intermediate results of no value to customer (nothing to run, to show)

    • Often delays and poor quality. Because first tangible results are only available with a successful test. This makes project management very difficult.

• Evolutionary model

  • 特点：

    • 通常从原型开始，系统的新版本从原型开始迭代

    • Development cycle is continued until user acceptance is reached

    • 不是一个线性的过程，而是a sequence of development cycles

  • 应用：

    • Vague user requirements or insufficient / missing technical baseline

    • Systematic reuse if systems are integrated from existing components or COTS(Commercial-off-the-shelf) systems

  • 缺点：

    • Systems are often poorly structured because final vision/needs/architecture are not known and agreed upfront

    • Unclear upfront resource estimation and allocation

  • 

• Spiral model（是evolutionary model的一种，主要特点是多了完善的risk评估）

  • 特点：

    • 通常从原型开始，系统的版本从原型开始迭代

    • Risks are explicitly assessed and resolved throughout the process

  • 应用：

    • Unknown user requirements or insufficient / missing technical baseline

    • Systematic reuse if systems are integrated from existing components or COTS(Commercial-off-the-shelf) systems

  • 缺点：

    • Systems are often poorly structured because final vision / needs / architecture are notknown and agreed upfront

    • Unclear upfront resource estimation and allocation

  • 

• Incremental model

  • 特点：

    • 增量开发，一点一点增加系统的功能和稳定性，让系统随时稳定运行

    • 在早期先把优先级最高的需求实现

    • 在一次（行）increment development中，需求是不变的，在开始时就固定，要增加需求要在下一次增量开发的时候才能加

  • 应用：

    • 易变的需求

    • 每次增量交付给用户，更好的实现项目控制

    • 敏捷开发

  • 缺点：

    • 最先开发的系统和服务会被测试多次

    • 一些敏捷开发不能用在复杂的系统和异地的团队

    • Often all principles of one methodology are used dogmatically

• IAS process model

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  • Project Execution (PE):

    • Software Development (SWD)

    • System Development (SD)

    • Concept Development (CD)depending on the process model class

  • Quality Aussurance (QA):

  • Testing the system and its components

  • Process inspection

  • Project Management (PM):

    • Planning and control of the process

    • Definition of work packages and milestones

  • Configuration Management (CM):

    • Ensuring the clear identification of the products

    • Version management of documents and source code files

• 敏捷开发：https://blog.csdn.net/xiajun2356033/article/details/81513957

  • 迭代

  • Scrum

    • Product owner：需要有专业知识，判断可否实现

    • Scrum Master：Responsible formaking the process run smoothly, forremoving obstacles that impactproductivity, and for organizing andfacilitating the critical meetings.不需要有专业知识

    • Team:开发团队

• Validation: do the right thing(customer requirements)

• Verification: do things right