● The （71） is a general description of the architecture of a workflow managemensystem used by the WFMC, in which the main components and the associated interfaces arsummarized. The workflow enactment service is the heart of a workflow system which consistof several （72） . In a workflow system, a process is specified using the process definitio 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 blinked by means of a directed arc. （71） A. waterfall model B. workflow reference model C. evolutionary model D. spiral model （72） A. workflow engines B. processes C. workflow threads （73） A. PERT diagram B. DFD C. Petri Net D. ER diagram （74） A. positions B. resources C. conditions D. places （75） A. transitions B. transformations C. transmitters D. changes