软件开发生命周期(三)


One element that distinguishes this process and that cuts across all four phases is an iteration. An
iteration
is a distinct set of work tasks, with a baselined plan and evaluation criteria that results in an executable system that can be run, tested, and evaluated.
The executable system need not be released externally. Because the iteration yields an executable product, progress can be judged and risks can be reevaluated after each iteration. This means that the software development life cycle can be characterized as
involving a continuous stream of executable releases of the system’s
architecture with a midcourse correction after each iteration to mitigate potential risk. It is this emphasis on architecture as an important artifact that drives the UML to focus on modeling the different view of a system’s
architecture.

如果说某个元素可以区分过程和四个阶段的分段，那么这个元素就是迭代．
迭代是带有基础计划和评价标准的一组不同的工作任务，目的是让一个可执行的系统能运行，被测试和被评估．这个可执行系统并不需要向外面发布．因为迭代产生的这个可执行产品，在每次迭代后，能正确判断进展及重新评估风险．这意味着软件开发生命周期可以被描述为一个连续的数据流，在每次迭代后产生一个中途修正的可执行版本的系统体系结构，以减轻潜在的风险．迭代作为在体系结构的一个重要工件，主要作用是引导UML注重系统体系结构的不同视点的建模．