“The goal of XPDL is to store and exchange the process diagram, to allow one tool to model a process diagram, and another to read the diagram and edit, another to "run" the process model on an XPDL-compliant BPM engine, and so on. For this reason, XPDL is not an executable programming language like BPEL, but specifically a process design format that literally represents the "drawing" of the process definition.” (Wikipedia, retrieved 14:27, 25 June 2010 (UTC))
In the WfMC workflow reference model described in the business process modeling article, XPEL relates to interface 1, defining exchange of process definition data between BPR tools, workflow systems and process definition repositories. XPEL is one of the possible serialization formats for BPMN, the Business process notation language.
The basic concepts that underlie XPDL were formulated for the Workflow Process Definition Language (WPDL), published by the WfMC in November 1998. Experience with WPDL led XPDL 1.0 in 2002. XPDL basically defined a new syntax using an XML schema. According to WfMC (retrieved June 30 2010), “XPDL is used today by more than 80 different products today to exchange process definitions. [...] XPDL is the most widely deployed process definition language and XML-based BPM standard, leveraged by broad spectrum of software applications ranging from ERP, call center and CRM, BI and BAM, process modeling and simulation, enterprise content management, as well as of course several of the leading workflow and BPM Suites. It has become the de facto global standard for workflow and BPM”.
See also: business process modeling, workflow, BPEL and BPMN
As of 2009, “BPMN has become the de facto standard for graphical representation of business processes. Unfortunately, the early versions of the specification provided no serialization format for a BPMN diagram. This was still true of the last approved version, BPMN1.2. The only standards-based alternative for serialization has been XPDL2.1, which incorporated the graphics and attributes of BPMN into the specification and XML serialization. In addition, XPDL2.1 defined subsets of BPMN, referred to as Portability Conformance classes, with software tools (XSL transforms) to test XML documents for conformance” (Robert Shapiro. BPMN Process Interchange (retrieved June 24, 2010).
“BPEL and XPDL are entirely different yet complimentary standards. BPEL is an "execution language" designed to provide a definition of web services orchestration. It defines only the executable aspects of a process, when that process is dealing exclusively with web services and XML data. BPEL does not define the graphical diagram, human oriented processes, subprocess, and many other aspects of a modern business process” (XPDL Support and Resources, WfMC, retrieved June 30 2010).