And the changes require redesign of the software, rescheduling of resources and some of the work already completed have to be redone or discarded and hardware requirements can be effected, too.

• 需求一经改变，软件就要重新设计，各种开发软件所需的资源就要重新计划，一些业已完成的工作必须重做或者直接舍弃。软件的硬件需求也会受到影响。