The new Web services dance

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Choreography standards do not spring up overnight. Indeed, the first crude set of choreographic symbols took more than 400 years and dozens of abandoned efforts to evolve into Hungarian dance master Rudolf von Laban’s widely accepted notation for representing the ordered and complex movements of dance.

The developers working on Web services   choreography standards expect to take less time than the dance master of yore, but the difficulty of the task at hand is much the same. They have to finesse technology nuances and please a variety of constituencies. At issue is how to define a standard way of letting business processes talk to each other during the course of a Web services transaction. Standardization would make Web services easier to develop — and deploy.

With Web services now, if a company wants to share parts of an application with a business partner, it can talk about the ports and operations it will expose using a Web Services Description Language (WSDL) file. The WSDL file would describe simple operations such as "get fare quote" or "book ticket." But the company has no standard way of talking about the business processes that govern all these operations. WSDL can’t tell an application not to bother trying to book a ticket before it’s received a fare quote — at least not in any standardized way.

To learn the business logic behind partner applications, developers must create a workflow document to which they can code. With Web services choreography, workflow descriptions are standardized. Instead of reading and manually coding to workflow specifications, developers could use typical development tools to handle this work.

Choreography standards put you "way ahead of the game," says Yaron Goland, a technologist at BEA Systems.    "You’re no longer sitting there trying to figure out, ‘Now if I call this particular interface, what the heck do I do next?’ "

BEA is working to incorporate Web services choreography features into its WebLogic Workshop development tool, and its competitors — IBM, Microsoft and Sun, for example — are doing the same with their wares.

And that’s where the problems begin.

On the dance card

In late June, Sun, along with BEA, Intalio and a number of other supporters, submitted a draft Web choreography specification, called the Web Service Choreography Interface (WSCI), to the World Wide Web Consortium (W3C). One month later, BEA, IBM and Microsoft   published an alternative, the Business Process Execution Language for Web Services (BPEL4WS). Now Sun, Microsoft and IBM are sparring over which specification will become the standard. On the outside are vendors such as BEA and Oracle that are urging a convergence of the two specifications.

Users also are interested in convergence because it would give them a greater range of tool choices and, more importantly, because the alternative could result in a nasty standards war. Choreography standards are becoming increasingly important as company and customer business processes get more intertwined, says Hao He, a software architect with Thomson Legal & Regulatory, a major law and tax information publisher in St. Paul, Minn.