W3C proposes XML linking technology

The World Wide Web Consortium (W3C) this week urged Web developers to implement its new "candidate recommendation" for adding links to XML documents. Dubbed the XML Linking Language, or XLink, the technology promises to advance XML's capacity in one of the Web's most crucial and defining characteristics: The ability to connect one page to another.

Extensible Markup Language (XML) lets Web page developers and other electronic-document authors use their own personal markup tags in such a way that XML-ready browsers can interpret them. XLink provides a mechanism for adding links between XML pages.

Currently, a Web surfer can use the familiar HTML hyperlinks to get to and from XML pages. But XLink provides a more sophisticated way of linking that accounts for the multilayered structure of XML documents.

"It's a bit more complicated than a traditional HTML linking mechanism," said W3C spokeswoman Janet Daly. "XML documents are like a bunch of Lego blocks, so you want to be able to refer to work in each of their sections in a clean way."

The XLink recommendation comes just a month after a related specification, XML Pointer, became a candidate recommendation. XML Pointer, or XPointer, addresses the discrete sections of an XML document.

Once an XML document is addressed with XPointer, Web authors can zero in on its components with the new XLink.

The XPointer specification builds on a slightly older XML addressing mechanism, XML Path Language (XPath), which also addresses parts of XML documents but with less specificity. XPointer also subsumes the W3C's ongoing XML address work that falls under the heading of XFragment.

"XPath was the start of being able to identify parts of an XML document," Daly said. "We need to build on that work with XPointer."

XLink's candidate recommendation stage will last three months, during which the W3C will urge Web authors to implement the specification, test it, and offer their comments. The subsequent "proposed recommendation" stage will evaluate the specification for an additional six weeks.

The XLink working group includes representatives from Sun Microsystems, Microsoft, Brown University, Fujitsu Laboratories, Arbortext and Commerce One.