Choreographing the Web services dance

Wouldn’t it be great if we had a way of managing the sequence of business processes that use Web services so that “the flow of tasks, the order in which they need to be performed, the type of data shared and how other partners are involved … [and] coordinate the various activities that occur within a business process, in order and at the right time for completion”?

That actual wording was from an announcement by IBM, Microsoft and BEA last August on the release of three new specifications (see links below).

Two of these specifications, WS-Coordination (an extensible framework for the coordination of actions of distributed applications) and WS-Transaction (for types used in WS-Coordination) address the communications of Web services. The third spec is a new XML-based description of business processes called Business Process Execution Language for Web Services, or BPEL4WS (which is actually a merge of Microsoft’s Xlang and IBM’s Web Services Flow Language).

BPEL4WS is the most profound of these specs and attempts describe business processes and business contracts. It is also (and this is important) proprietary which means that it could have licensing implications further down the road for all of the early adopters. IBM has said that it wants BPEL4WS to be free but the other partners haven’t committed yet.

But BPEL4WS isn’t the only game in town. Nope, there’s also the Web Services Choreography Interface or WSCI (pronounced “whiskey”) which has the support of BPMI.org, Commerce One, Fujitsu Limited, Intalio, IONA, Oracle Corporation, SAP AG, SeeBeyond Technology Corporation, Sun Microsystems, and BEA (who, as a BPEL4WS co-author, are thus sitting squarely on the fence). Even more importantly, WSCI is now on the World Wide Web Consortium’s standards track.

Other Web services standards that are involved in the whole WSCI business process specification and management world include WS-Security, WS-Reliability and Web Services Conversation Language (or WSCL to manage and maintain state information across a Web services dialog).

The latest volley in this arena was IBM’s announcement in February that it would be bundling a BPEL4WS workflow engine with WebSphere Application Server Enterprise and WebSphere Studio Application Developer Integration Edition.

Add to that the recent announcement that Microsoft, IBM and BEA Systems are going to submit BPEL4WS to the Organization for the Advancement of Structured Information Standards (OASIS) and the race to see whether BPEL4WS or WSCI wins is on.

We’re in for an interesting year in the evolution of Web Services and the way these standards play out will have a huge impact on the future of Web applications.