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Members offer glimpse inside WS-I consortium

In an interview, leaders of the WS-I talk about the inner workings of the group and details of the new Basic Profile guidelines for Web services interoperability.

BOSTON -- Throw 150 software engineers together in a room to discuss interoperability standards and what do you get? A raging debate, certainly. A consensus is a little trickier.

For the vendor-backed Web Services Interoperability Organization (WS-I), getting a group of engineers to reach a consensus was a matter of deciding what was critical for making Web services specifications work with one another and dropping debate on everything else.

The result was Basic Profile 1.0, a set of guidelines for Web services interoperability that was released at last week's XML Web Services One conference. In a wide-ranging interview with, WS-I board members from IBM Corp. and Oracle Corp. and the chairman of the Basic Profile working group talked about the inner workings of the consortium and how users of Web services technology will soon be able to judge for themselves whether solutions are truly interoperable.

"There's nothing magical about WS-I," said Rob Cheng, Oracle's representative on WS-I's 11-member board. "There was a need. There was a demand. There was motivation to do it. So we got together and did it."

The group, formed in February 2002, got off to a rocky start by excluding Sun Microsystems Inc. from its board, but that was rectified when Sun was elected by member companies to a two-year term on the board in March.

Big vendors vs. small vendors

Because of the organization's "one company, one vote" policy, large companies can't dominate smaller members, said Tom Glover, chairman of the WS-I and a program manager with IBM's Web services standards software group.

"We've got small companies that have a lot of influence," he said. "We've got large companies that frankly have almost none."

Cheng said some of these big companies are there to make sure they can be early adopters if they see an opportunity. "They don't care to contribute the resources to make it happen, but they want their guys to hear it so they are ready to put it in a product."

From a technical perspective, the working group avoided wasting time talking about issues that were not germane to the mission of achieving interoperability among the core Web services specifications of SOAP 1.1, WSDL 1.1, UDDI 2.0, XML 1.0 and XML Schema.

SOAP encoding dropped

Chris Ferris, chairman of the Basic Profile working group and a senior software engineer at IBM, said a perfect example was Simple Object Access Protocol (SOAP) encoding, a method of encoding "type" information in XML messages. Members argued about what type systems to use between different development platforms.

How did they resolve this issue? The working group dropped the idea of SOAP encoding interoperability in favor of XML Schema as the type system for Web services. Ferris said that, at the time of that debate, XML Schema was finished, published and was "precisely written."

"We just carved out that whole section of the SOAP spec and said, 'Let's not go there,'" Ferris said.

The ambiguity of WSDL

That theory played out during other discussions, including those involving the Web Services Description Language. Ferris said that because WSDL was meant to be broadly extensible, there were "a lot of creative interpretations" by vendors. "It was like reading a different book."

"Fully 44% of the [interoperability] issues we tackled, of the 200-odd issues, were around the WSDL specification," Ferris said. The working group had to clarify WSDL and "clean up the ambiguity aspects of it," such as how to use it with SOAP and the Universal Description, Discovery and Integration (UDDI) registry.

This will likely be the case when the WS-I tackles interoperability for other Web services specifications, Ferris said. Some functions, or options, of an underlying specification will be "must options" for vendors to follow. Other functions can be added as a service to users, "but when you do, you're on your own" in terms of interoperability with other products, Ferris said.

Not a standards body

One area that the WS-I won't go into is creating standards themselves.

"We don't write the standards. We just reference them," Glover said. "We provide advice on how to put them together and use them productively -- if interoperability is what you're trying to achieve."

Glover and Ferris predicted that WS-I has at least 10 years of work ahead to fine-tune various Web services specifications in areas such as security, reliable messaging, management and orchestration. Cheng said the order in which these issues will be handled rests entirely with the demands of WS-I's 170 member companies and the implementation issues that arise as they develop applications that can deliver Web services.

Next in line for the WS-I is security interoperability. Ferris said a planning group has already outlined the scope of the effort and is awaiting the final release this month or next of the Web Services Security specification by the OASIS standards group. The focus of the security profile, which Ferris predicted would be complete within a year, will be to narrow down options within the specification to the "must haves."

Free testing tools

All this work will be for naught, however, if end-user customers aren't convinced that vendor solutions are compliant with the interoperability guidelines issued by the WS-I. That's why the group plans to release a set of free testing tools in the fall that will allow customers to gauge whether vendors' claims are valid.

Ferris said a monitoring tool will allow users to capture message traffic between a Web services client and the provider of the service and then archive that data in a log file. A second tool, an analyzer, will take the log file, the WSDL description and the UDDI registration and analyze those Web services artifacts against a set of test assertions that are part of the Basic Profile. This will tell a user whether a particular Web service "instance" conforms to the interoperability profile.

The tools, which are currently in their fourth beta, will be available on the WS-I Web site in the fall for Java and C#.


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