BPMN, XPDL and BPDM
BPMN (Business Process Modeling Notation) (as of this writing, 2007-03-27, the latest version is 1.0, the definition of which was published at 2006-02-06) is a workflow modelling definiton which uses abstract graphical notations, developed to be able to express business processes with genric workflow concepts. It may be used to produce an execution or interchange lelvel language (e.g. XML based languages such as XPDL or BPEL). In that sense, it is said to be "language neutral". It uses graphical notations of "control flow", artifact (data object), messages and swim lane paradigm for Roles.
XPDL (XML Process Definition Language) v. 2.0 (WfMC-TC-1025, v 1.14 final, 2005-10-03) is apparenlty an XML profile of BPMN which has 1:1 correspondence. This is intended to be used for process definition interchange standard. WfMC also developed Wf-XMLwhich apparently tells the engine how to install procsses received by XPDL, WS-BPEL, etc.
BPDM (Business Process Definition Metamodel) is currently an OMG (Object Management Group) standard proposal which is supported by the U.S. National Institute of Standards and Technology (NIST). The model aims to be able to express business processes (including human participants) based on OMG's MOF (Meta Object Facility) and UML.
