More and more, eXtensible Markup Language (XML) is being seen as life-after-HTML, and it took a step further forward yesterday with the World Wide Web Consortium’s (W3C) release of version 1.0 of the XML specification as a W3C recommendation. A recommendation means the members of the W3C have reviewed the spec and it is stable, which is as far as each spec goes within the W3C. XML was developed by the W3C’s XML working group, and it is a version of the ISO-standardized Standard Generalized Markup Language (SGML) designed for use on the web. It is regarded as both the successor to HTML, the development of which has been hampered at times by vendors writing browser-specific extensions, but also complementary, as XML offers a more broad-based and versatile markup language. Web developers must be hoping XML is not held hostage to similar wrangling that has befallen HTML, but Dan Connolly, W3C architecture domain leader and XML activity lead said there are safeguards built into the XML spec to help prevent this. For instance, if an XML document is processed and an error is found, developers have to stop and correct it before moving on. In that way it is radically different from HTML, says Connolly. XML is not just a long list of tags, he adds. XML, as the name suggests, is extensible. It enables developers to make up their own tags as required, which can be used to identify a particular piece of text as belonging to a particular group. As well as extensibility, XML is said to retain some of SGML’s basic features, such as complex structures, validation and human readability. It is also said to backwards-compatible with most features of HTML, which is currently on version 4.0. As long as there is a requirement for things like paragraphs, lists and headings – which there will be – then HTML has a part to play, says Connolly. But XML is tailored towards building more complex structures while the language itself should make the structures more easily discernible by developers. The original XML spec was co-authored by Jean Paoli, the product unit manager at Microsoft Corp’s Weblications group, Tim Bray, principal at Textuality and consultant to Netscape Communications Corp, and CM Sperberg-McQueen, editor in chief of the Text Encoding Initiative at the University of Illinois at Chicago. A W3C recommendation is the last of three review stages, the previous two being working draft and proposed recommendation.
