W3C Approves XML Namespaces

By RICHARD KARPINSKI

The W3C this week formally approved XML Namespaces, an addition to this rapidly maturing technology that prevents conflicts in naming XML data sets.

The recommendation, which was widely supported among XML vendors and expected to be quickly implemented in parsers and browsers, lets developers qualify element names uniquely and thus avoid collisions between XML elements with the same name.

This is especially important as XML becomes a more common Web data format and developers and applications look to combine and integrate XML data from multiple sources, for instance in a search or e-commerce application, said J.P. Morgenthal, analyst with NC Focus.

"Namespaces help to eliminate clashes of element names," Morgenthal said.

Namespaces can tie a particular XML grammar to a company or industry group. For instance, in a business-to-business purchasing application, it would be important to amend an <invoice> tag with a Namespace that ties that data set to a particular vendor versus another.

"I'm positive that when Barnes and Noble and Amazon.Com start using XML, they'd both have a <book> tag. Without Namespaces, you as a user would have no idea where that data was coming from, so you couldn't compare prices or do other things with the data.," said David Wascha, Microsoft product manager for platform marketing.

That greater precision also makes it possible for developers to re-use and combine XML data sets, rather than have to create all new sets due to concerns about potential tagging conflicts.

The addition of Namespaces in some sense demonstrates the relative immaturity of XML. The idea of Namespaces, or scoping, is standard in conventional programming, said Microsoft's Wascha. "You can't have two variables with the same name and a different function," he said.

"You tell people what Namespaces does, and they're like, 'big deal,' " said Wascha. "But you need to make that concept mandatory in XML to do real applications. People in some cases have been attributing a lot more maturity to XML than has really been there up to now."

Namespaces work by qualifying XML element names with a prefix tied to a unique Web address, or URL. The prefix is similar to a telephone area code, which lets identical phone numbers be used in different cities, the W3C said.

Namespaces will pave the way for future XML developments, including data exchange based on the Resource Definition Framework. Namespaces play a crucial role in the W3C's ongoing effort to reinvent HTML as an XML application, according to the W3C.