Keith Mantell at IBM wrote an article on using UML and MDA concepts to gen your bpel. See:
He creates a UML profile that has the semantics to represent bpel and then discusses making a map from the model to the bpel code. The base process is represented as a class and the orchestration is modeled as an Activity Diagram.
All in all, it is an interesting concept. One concern that I have is that people don't try too hard to shove a square peg (UML) into a triangular hole (SOA & BPEL). The base UML models were developed some time back and don't always represent the concepts that we need. For instance, I use a Service-Based Sequence Diagram rather than Activity Diagrams to represent orchestrations... just seems easier.