In xpdl ,WorkflowProcess is mainly made up of activities and transitions.In my view ,this structure does not describe the nature of the system.
I think that ,a system is composed of two parts,first is the business sub-system, and then the workflow sub-system. When the system run, the "control flow" exchanges between the business sub-system and the workflow sub-system.
For example , after a actor commits a form and completes his work, the workflow sub-system gets the control. It is now the workflow sub-system's duty to determine the next business step.
After the workflow sub-system makes its decision, the business sub-system gets the control,and waits for another actor to join the business.
So, in my view ,the WorkflowProcess is made up of Activities?Synchronizers and Transitions. Activity represents the business logic, the Synchronizer represents the workflow logic, and the Transition represents the control flow. my workflow process diagram is as follows:
It is exactly a Petri net ,isn't it?
By the way, i think that the XPDL is too complex. I have simplified and extended it.
I have provided a designer, a simulator and an open source engine. The attatchment is the picuture of the designer and the workflow process simulator. You can download here
www.fireflow.org/download.html.
