Specifying Business Collaborations over Web Services
The WS* stack has BPEL that provides the description of a process controlled by a single participant. This does not really address how to specify business collaborations -- multiple coordinated processes.
At AIAG (Automotive Industry Action Group) we are working on a Model-Driven approach to Web Services collaborations. It is a work in progress but seems to provide some of the missing pieces. We call it Business Collaboration Specification (click the link to see a primer PowerPoint)