- Waterfall Lifecycle This model supports large and complex projects in which the requirements are well defined. It adopts sequential approach from requirements analysis through design, construction, testing and application deployment. 2. V Lifecycle 适合对系统可靠性要求比较高的项目。强调测试。 This model supports new product development or large enhancement projects when the size and complexity of the system is large enough to have a multilayered design. Adopt this model when the requirements are well understood, complete, and stable and the technology & architecture of the solution is clear and visible. SOW(UAT plan)---Requirement(System Test plan)---Architecture Design(Integration Test plan)---Low Level Design(Unit Test Plan)----Construct(V model bottom) ---Unit Test ---Integration Test ---System Test ---UAT 2.1 Feature Concurrent Phases or Activities Mandatory unit testing Easy to plan Emphasizes and encourages Verification and Validation at all phases 2.2 Disadvantage Does not handle iterations Changes are expansive More documentation and mandatory sign-off to move out of the phase Like waterfall model, Product is not visible until the end 3. Staged Lifecycle 架构已经定义好，允许分阶段的Low Level Design 和实现。 In this model, certain intermediate work products (incremental deliveries) will be delivered to the client before final delivery of the entire application. It supports product development or large enhancement projects when the requirements are not well understood and skeptic on stability of requirements. The Staged Lifecycle is best suitable for the development of new products or for executing large enhancements. Cycle: Low level Design --- Build --- IT,ST,REL,AT 3.1 Feature when the requirements not well understood, not complete or not stable. when there is a need for continuous deliveries from customer side. when allow incremental design and implementation in a number of stages. allow for specification changes in the subsequent release 3.2 Disadvantage need careful planning extra overhead on multiple release determining stage dependencies is difficult 4. Iterative Lifecycle This model supports large and complex projects with the following characteristics: Where continuous quality check & high degree of requirements management is needed through out the project. Where the requirements will change considerably and the environment is not stable. Where it is not possible to specify the requirements in enough details upfront. Where delivering on time is essential, irrespective of the functionality. cycle: Envisioning（构思） --- Design ---Build --- Test --- Release & Deployment 上面cycle中每个阶段中分多次迭代。 5. Rapid Applicaton Development Lifecycle