Standards body the World Wide Web Consortium (W3C) today recommended XHTML (Extensible Hypertext Markup Language), the first of a new family of Web authoring languages written in XML (Extensible Markup Language). XML, also a W3C recommendation, lets anyone define new Web languages and tag digital documents to make it easier for computers to read and manipulate them.
Fortunately for Web markup pioneer HTML (Hypertext Markup Language), XHTML is "backwards-compatible"--meaning that Web developers will not have to rewrite their pages in the new markup language. In addition, most browsers currently in use will be able to read XHTML documents--such as the W3C's home page--without an upgrade.
Web authors theoretically could ignore this sweeping change in Web programming. But they probably won't want to.
XHTML breaks new ground on the Web, giving authors a way to mix and match various XML-based languages and documents on their Web pages. It also provides a framework for nontraditional Web access devices, from toasters to television sets, for identifying themselves and their capabilities to Web servers, pulling down only information that the devices can display.
XHTML had an unusually long gestation period. Introduced in August, the proposed recommendation encountered a firestorm of criticism from developers who objected to the way it handled namespaces, or the way computers distinguish tags from different programming languages that mean different things but bear the same name.
The recommendation for XHTML proposed three namespaces. Developers countered that it should have one. The W3C sent the proposal back to the drawing board and, in a victory for the developers, it was approved with a single namespace.
The six weeks that typically separate a proposed recommendation from a final recommendation turned into five months.
"It was worth the wait," said W3C spokeswoman Janet Daly. "XHTML will serve as a firm foundation for the Web of the future. What it allows us to do is really build a functional bridge between the HTML world into the XML world that's growing today. It's a first step in providing an easy path to XML for regular HTML content producers."
In addition to making Web pages more "extensible"--that is, letting them absorb markup tags and documents from XML-based languages--XHTML will mandate "markup conformance," forcing Web developers to hew closely to rules on tagging and case-sensitivity. HTML, by being more flexible with tagging, is easier for people to write but more difficult for machines to read.
Contributing to the language's ease of use is that XHTML tags are based on traditional HTML tags. Web authors will have to write more carefully, but they won't have to start from scratch.
The "device profiling" aspect of XHTML is still under construction. Dubbed "composite capability preference profiles" (CCPP), it would let a device such as a cell phone identify itself to a Web server, describe its limitations, and download only the information it's capable of displaying. CCPP works because XHTML documents can be split into modules that can be downloaded separately.
The W3C is working on CCPP in collaboration with the Wireless Access Protocol Forum, among others.
Companies and organizations pledging support for XHTML upon its release include CWI, Ericsson, Hewlett-Packard, the HTML Writers Guild, IBM, America Online's Netscape Communications unit, Opera Software, Phone.com, Stack Overflow and the ZOT Group. Stack Overflow today released Mozquito Factory, an XML authoring environment for XHTML.
In other XML-related news, Microsoft released a preview of its XML parser, and a San Francisco start-up said it would propose to an international standards body a new transport protocol for XML data.
Microsoft's new parser adds support for parts of the W3C's Extensible Stylesheet Language Transformations (XSLT) and Extensible Markup Language Path Language (XPath) recommendations for styling XML documents. Microsoft said this is the first of many such parser releases to come, and more complete support for XSLT and XPath is on the way. The parser is the piece of software responsible for interpreting tags in a browser or other document reader.
"What we've developed is a standard way of getting XML back and forth," Malamud said in an interview. Malamud conceded that XML can travel via HTTP, but he said there is no consensus on how to do that.
Invisible Worlds will present its proposal at the task force's next three-times-yearly meeting, in March. News of its proposal was first reported by The Wall Street Journal.