XPDL

The XML Process Definition Language (XPDL) is a format standardized by the Workflow Management Coalition (WfMC) to interchange business process definitions between different workflow products, i.e. between different modeling tools and management suites. XPDL defines an XML schema for specifying the declarative part of workflow / business process.

XPDL is designed to exchange the process definition, both the graphics and the semantics of a workflow business process. XPDL is currently the best file format for exchange of BPMN diagrams; it has been designed specifically to store all aspects of a BPMN diagram. XPDL contains elements to hold graphical information, such as the X and Y position of the nodes, as well as executable aspects which would be used to run a process. This distinguishes XPDL from BPEL which focuses exclusively on the executable aspects of the process. BPEL does not contain elements to represent the graphical aspects of a process diagram.

It is possible to say that XPDL is the XML Serialization of BPMN.

The Workflow Management Coalition, founded in August 1993, began by defining the Workflow Reference Model (ultimately published in 1995) that outlined the five key interfaces that a workflow management system must have. Interface 1 was for defining the business process, which includes two aspects: a process definition expression language and a programmatic interface to transfer the process definition to/from the workflow management system.

The first revision of a process definition expression language was called Workflow Process Definition Language (WPDL) which was published in 1998. This process meta-model contained all the key concepts required to support workflow automation expressed using URL Encoding. Interoperability demonstrations were held to confirm the usefulness of this language as a way to communicate process models.

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