The (71) 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 (72) . In a workflow system, a process is specified using the process definition tool. Usually, processes are defined in terms of a (73) , which consists of (74) indicated using a circle, and (75) shown as a rectangle. These two components can be linked by means of a directed arc.
（72）处填（）。
A．tasks
B．processes
C．workflow threads
D．workflow engines
