BPML was useful to OMG in order to enrich UML with process notation[citation needed].
In view of the lack of market acceptance, the BPMI dropped support of BPML in favor of BPEL4WS.
In addition, BPEL is often tied to proprietary implementations of workflow or integration broker engines.
Whereas, BPML was designed, and implemented, as a pure concurrent and distributed processing engine.
It was designed to be semantically complete according to the Pi-calculus formal representation of computational processes.