●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.
（71）A．waterfall model
B．workflow reference model
C．evolutionary model
D．spiral model
（72）A．workflow engines
B．processes
C．workflow threads
D．tasks
（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