Stevenson, WA: It's always refreshing to attend a deeply technical conference, at which the experts instruct each other, disagree publicly, and challenge one another's opinions. Instead of showing off shiny new functionality or imperfect features polished to a mirror surface, the developers at the Applied XML Developer's Conference are demonstrating the problems yet to be solved in XML and Web services.

Still, the technical presentations make it clear that they agree on fundamental development truths: the data outlasts the code, you won't find much reality in any industry spec, and simplicity is always better than (even elegant) complexity.

One weakness upon which most presenters agree is the ineffectiveness of XMLSchema, which Tim Bray, Director of Web Technologies at Sun Microsystems (and co-inventor of XML) described as "totally beyond its 'Sell-By' date."

Chris Anderson, an architect on the MS Windows Client Platform team working on the technologies code-named "Avalon," says that developers "hate systems that force XML to be more than data." His answer: XAML, which "provides a format to facilitate between developers and designers ... a unified way to build applications to leverage markup."

Sam Ruby, Senior Technical Staff Member in the Emerging Technologies group at IBM, spent 45 minutes showing other experts how "the standards don't reflect reality; reality has moved on," particularly in regard to Unicode. Even when default encodings for HTML, XML, and Microsoft encodings are different, and XML Namespaces requires that the URI examples be considered distinct, System.Uri.Equals may return "true."

Not every aspect of XML is judged to be a potential disaster — far from it. Two presentations have demonstrated how XML is enabling solutions in the real world: one from the U.S. Department of Defense on using XML for Navy Missile Systems, and a presentation from Corillian's Scott Hanselman and Patrick Cauldwell about effectively using XML in financial systems.

Some XML technologies have yielded long-term results, or they will. "We had pretty ambitious goals for SOAP," explains Don Box, architect at Microsoft in the Distributed Systems Group working on Indigo. "The one thing we wanted was an extensibility mechanism other than XML's 'throw [stuff] anywhere you want.'" Today, says Box, SOAP's header extensibility model is the conceptual basis for the serialization engine for .NET. Yet "the single most important thing we [previously] left out was ws-mex [metadata exchange] or something like it," says Box. It's now a core part of Indigo, and "every SOAP endpoint will support ws-mex by 2007."

And there's plenty of dissent among the experts, none of whom are shy with their opinions. Even when they agree on the problems, they don't always agree on the solutions, with the sharpest division between those who prefer APIs and programming models versus data streaming. Bray says, "WS-Eventing is missing the boat." Box said, "If this entire experiment fails, I think the fingerprints [on the knife] will be on WSD and XSD."

But each speaker has an underlying theme of "keep it simple." Bray exhorts developers to create solutions based on the MPRDV approach: the "minimum progress required to declare victory." Add functionality only when you have to, and based on real experience. "Committees going into rooms do not invent the future," he says. Anderson reminds developers that "XML is cardboard" — the transport medium for the "important stuff" you're moving from place to place.

That's not to say that developers are down on XML — not hardly! These folks are the ones immersed in the technology and clearing the path for those to follow. "They're shining the light in the dark corners," remarked one conference attendee. Because of the technology sharing, one long-outstanding bug that Sam Ruby demonstrated on the MSDN site was fixed within two hours.

Despite XML's imperfections, each presenter sees the benefits that XML and Web services have brought, from RSS ubiquity to interoperability to the importance of internationalization. On her blog, Rebecca Dias, Advanced Web Services Product Manager at Microsoft Corporation said, "Everyone generally agrees that Schema has it's shortcomings, but it is facilitating huge amounts of value for customers. Thousands of business documents today are based on a schema. So, is XML Schema a failure?"