BPMN Process Interchange

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. These subsets allowed vendors a stepping-stone approach to full conformance and users the chance to benefit from model interchange for high-level designs early in this process.

Some people have claimed portability by the use of BPEL. This is a misrepresentation. BPEL does not support all legal BPMN diagrams and does not contain the graphical information required. Nor does BPEL represent a pathway for model interchange at the design level, where it is commonly required to support round-trip between business analysts and IT programming specialists, or model interchange between high-level models and simulation technology.

BPMN2.0, when approved, will offer an XML serialization. More is required to achieve process model interchange. The specification contains many new ideas; it is not simply a document presenting a serialization of BPMN1.2. Some of the new ideas have yet to be proven in practice. Some of the process model extensions increase the complexity of the models. There is no clear distinction between the attributes required for execution and those for high level design such as what would be used by a business analyst.

Portability Conformance classes will need to be defined for BPMN2.0 in order to create the possibility of any kind of round-trip interchange in the next few years. Validation tools for checking XML documents for structural integrity will be required. These should be developed both for the proposed BPMN2.0 XML serialization as well as the XPDL2.2 serialization (an extended version of the existing XPDL2.1 serialization). XPDL strives for backward compatibility so that older XML documents that were previously conformant will still be usable.