面向对象软件方法学.ppt

Modules don’t fit We don’t expect students to read this chart. It is an abstract view that shows the many to many relationships among the symptoms and root causes, and between the root causes and practices. It is meant to indicate that we have done the mapping, so they don’t have to. Animation notes: This animation is automatic. It shows the tracing from symptoms to root causes to the best practices we will discuss. R: Requirements Analysis D: Design C: Coding, Unit Testing T: Subsystem and System Test Iterative processes were developed in response to these waterfall characteristics. With an iterative process, the waterfall steps are applied iteratively. Instead of developing the whole system in lockstep, an increment (that is, a subset of system functionality) is selected and developed, then another increment, etc. The selection of the increment to be developed first is based on risk, the highest priority risks first. To address the select risk(s), a subset of use-cases are chosen. The minimal set of use-cases that will allow objective verification (i.e., through a set of executable tests) that this risk has been addressed, is developed. Then the next increment is selected to address the next highest risk, and so on. The waterfall is thus applied at the increment level and the system evolves incrementally. In the iterative approach, the waterfall is applied to a single increment of the system at a time. Each iteration produces an executable. Animation note: The graphic automatically wipes right The earliest iterations address greatest risks. Each iteration produces an executable release. Each iteration includes integration and test. Iterations help: resolve major risks before making large investments. enable early user feedback. make testing and integration continuous. focus project short-term objective milestones. make possible deployment of partial implementations. Iterative processes were developed in response to waterfall characteristics. With an iterative