The（1） is a general description of the architecture of a workflow management system used by the WFMC, in which the main components and the associated interfaces are summarized. The workflow enactment service is the heart of a workflow system which consists of several（2）. 空白（1）处应选择（）

• A、waterfall model
• B、workflowreference model
• C、evolutionary model
• D、spiral model