The World Wide Web Consortium (W3C) today recommended "Namespaces in XML," which will let browsers interpret more than one XML-based language in a single document without confusing different elements with the same tag names.
Extensible Markup Language is a metalanguage that lets authors create industry- or discipline-specific markup languages for the Web. MathML, for instance, has tags that are tailored to produce mathematical operations within the browser. Synchronized Multimedia Integration Language (SMIL--pronounced "smile") is a W3C-recommended XML-based language that synchs images, text, and sound on the Web.
It is not hard to imagine a Web document that would use both MathML and SMIL. If the two languages had tags with the same names, it could wreak havoc for the browser.
Today's namespace recommendation, proposed in November, provides a way for the browser to distinguish those homonyms.
With XML Namespaces, Web authors will have more freedom to mix and match XML-based languages. This more modular approach will let authors reuse existing languages instead of writing new ones from scratch.
The namespaces recommendation uses the Web addressing infrastructure to mark each tag with a unique address. The W3C likens the effect to that of a telephone area code, which lets identical seven-digit phone numbers be used in different regions.
The value of the URL to the recommendation is primarily its uniqueness, and the browser won't necessarily need to access the document located at the identifying address.