Wf-XML and a RESTFul Wf-Store
One requirement for GEOSS and OWS-5 is to seamlessly interface with several workflow engines (BPEL, OpenWFEru and SensorML). These workflows will have to be fully accessible as resources over the web and discoverable.
A lot of work has been done in that area by the Workflow Management Coalition Group (WfMC). Wf-XML 2.0 is the current XML-based protocol for run-time integration of process engines. Several issues are hindering the effort. SOAP 1.2 is still not supported by SOAP4R and the Ruby code generated from the WSDL file is questionable. And by the way, WSDL 2.0 has just been approved by the W3C.
Wf-XML relies on the OASIS Asynchronous Protocol (ASAP) which is still in draft form while the W3C is proposing WS-Addressing. If we are there, then might as well look at the WS-Notification group of specifications… grrrr! Does not look easy…
Plan B is to take a step back and look at a RESTful approach and consider workflows as web resources. It ought to be straighforward to create an entry for a workflow, add versionable definitions for that workflow and create instances to run. The proposed approach is to create a RESTful access to those collections and publish the services using the new Atom Publication Protocol.
These workflows ought to be searchable via an OpenSearch web service that would output atom feeds.
Notifications could happen using Twitter or any simlar Publish/Subscribe mechanism.
A simpler SOAP service could be implemented later on top of that architecture.