XPDL, a competitor of BPEL (Chapter 5) and BPML (Chapter 6), is the WfMC’s XML process definition language. In the WfMC reference architecture, XPDL is the interface between process definition tools and the enactment service. Specifically, processes designed in a tool are exported in XPDL format and loaded into the enactment service for execution, XML being a suitable external representation. Other purposes of XPDL are to move process definitions between tools. A process definition tool should have both export and import capabilities: export to XPDL, and import from XPDL.
The WfMC does not prescribe a standard graphical notation language. Exactly how a given process definition tool represents a process visually is immaterial; what is essential is its support for the import and export of XPDL.
The basic notions of XPDL and their relationships are depicted in Figure 7-3.
The topmost entity is
Package, which defines an entire
application or a major system. A package consists of one or more
workflow process definitions and supporting entities, which include
participants (a list of human or system actors that perform key
process roles), applications (programmatic components called by the
process), and data fields (also known as workflow-relevant
A workflow process, the central construct of XPDL, consists of one or more activities and a set of transitions. The mathematical idea of directed graph underlies this conception; each activity is a graph vertex; ...