Getting Wired: The ever-expanding empire of XML

The W3C making XML its central focus reflects broader trends in corporate computing

The W3C making XML its central focus reflects broader trends in corporate computing

The home page of the World Wide Web Consortium (W3C) is exemplary in its clean lines and simple design. But its content can sometimes seem a bewildering alphabet soup of CC/PP, Pics, Tag, WAI, WebCGM and the rest. What this love of abbreviation tends to obscure is that almost all of the W3C's work revolves around one central technology.

This is not, as you might think, the HTML that underlines and originally defined the World Wide Web, but its smarter younger sibling XML. In fact, the W3C is keen to wean the Web developer community off "classic" HTML - HTML 4 - completely.

Its preferred Web markup flavour is XHTML. As its name hints, this is a reformulation of HTML as a formal application of XML, rather than as a rather rough-and-ready application of the more complicated Standard Generalised Markup Language (SGML), as HTML was. The advantage is that XHTML retains much of the strength of the original SGML without sacrificing the key properties of HTML - notably legibility and relative ease of use - that powered it and the Web to such a rapid and total domination of the online world.

But, from a conceptual viewpoint, replacing HTML with XHTML is almost a trivial application of XML. XML's real power is to enable the ready exchange of data between heterogeneous computing systems - a crucially important activity that lies at the heart of all e-commerce and ultimately all business too.

Some measure of XML's growth can be found in the astonishing size of Robin Cover's resources covering every aspect of XML. In particular, the list of many hundreds of current applications of XML to specific areas - often commercial ones - is testimony of just how powerful and flexible the language is.

But the XML story is more than just a matter of numbers. Its steady march to the centre of the Web - which both explains and justifies the W3C's increasing concentration on this area - is emblematic of broader trends within the computing world, particularly that of corporate computing.

For example, XML's rise signals the definitive defeat of proprietary file formats. And by allowing, in theory, any kind of data to be exchanged between any kind of computer, it also undermines the importance of the details of those computers - notably which operating system they run. This represents a generalisation of the Web's ability to shield users from any consequence, or even knowledge of the details of the underlying computers that serve HTML pages.

In fact, just as the appearance of the HTML and HTTP standards signalled a shift towards completely open protocols for information interchange, so the emergence of XML can be regarded as part of the larger move towards open and non-proprietary standards visible elsewhere in the increasing adoption of open source software such as the Apache Web server and the GNU/Linux operating system.

Against this background, the W3C's work on XML can be seen as perhaps the most important manifestation of its commitment to open, non-proprietary protocols and of ensuring that the Web remains a unified system not under the effective control of any one organisation. This alone makes its XML work important, and to a large extent answers the rhetorical question I posed a few weeks back about the role of the W3C in today's online world.

As the brief introduction to XML indicates, the W3C began work on XML in 1996, culminating in the 1998 XML 1.0 recommendation. Phase 2 of its work, until September 1999, was chiefly notable for the introduction of XML namespaces. This was a crucially important move that allowed several applications of XML to be used and mixed together. This opened the door to far more complex kinds of XML, and made possible the advanced uses of XML that are currently under development.

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