ERCIM News No.41 - April 2000 [contents]

XHTML 1.0 for Device-Independent Web Access

by Steven Pemberton

The World Wide Web Consortium (W3C) has released the XHTML 1.0 specification as a W3C Recommendation. This new specification represents cross-industry and expert community agreement on the importance of XHTML 1.0 as a bridge to the Web of the future. A W3C Recommendation indicates that a specification is stable, contributes to Web interoperability, and has been reviewed by the W3C membership, who favour its adoption by the industry. XHTML 1.0 was developed in a W3C working group chaired by CWI researcher Steven Pemberton. 

HTML currently serves as the lingua franca for millions of people publishing hypertext on the Web. While that is the case today, the future of the Web is written in W3C’s Extensible Markup Language (XML). XML is bringing the Web forward as an environment that better meets the needs of all its participants, allowing content creators to make structured data that can be easily processed and transformed to meet the varied needs of users and their devices.

In designing XHTML 1.0, the challenge was how to design the next generation language for Web documents without making obsolete what is already on the Web. The answer was to take HTML 4.0, and rewrite it as an XML application. In simple terms that means making the HTML a well-formed XML document where start and end tags are always there and match precisely. Empty elements have to use the correct syntax. XHTML 1.0 allows authors to create Web documents that work with current HTML browsers and that may be processed by XML-enabled software as well. Authors writing XHTML use the well-known elements of HTML 4 (to mark up paragraphs, links, tables, lists, etc.), but with XML syntax, which promotes markup conformance.

The benefits of XML syntax include extensibility and modularity. With HTML, authors had a fixed set of elements to use, with no variation. With XHTML 1.0, authors can mix and match known HTML 4 elements with elements from other XML languages, including those developed by W3C for multimedia (Synchronized Multimedia Integration Language – SMIL), mathematical expressions (MathML), two dimensional vector graphics (Scalable Vector Graphics – SVG), and metadata (Resource Description Framework – RDF).

In addition to its extensibility, moving from HTML to XML via XHTML 1.0 lays the foundation for making Web content available to millions more users. People browsing the Web with cell phones or other mobile devices want Web content tailored to their needs. People with disabilities need ways to transform content into accessible formats.

XML documents can already be transformed using Extensible Stylesheet Language Transformations (XSLT), and rendered using independent style sheets such as CSS style sheets. XHTML 1.1, already under development, coupled with device-specific style sheets and Composite Capability/Preference Profiles (CC/PP) - a protocol which allows a user to describe both user preferences and device capabilities - will bring mobile and other devices to the Web as full participants.

The XHTML 1.0 Recommendation was written by members of the HTML working group, which includes key industry players such as Ask Jeeves, CNET, Gateway 2000, CWI, GMD, Hewlett-Packard, HTML Writers Guild, IBM, JetForm, Microsoft, MITRE, Philips Electronics, Phone.com, Quark, Stack Overflow, Sun Microsystems, and WebTV Networks.

CWI always has been at the forefront of developments on the Internet and the World Wide Web. In 1988 CWI was Europe’s first non-military Internet site, and became a Dutch and European backbone site. Since then it was involved with the development of the Web programming language Python, HTML, CSS (Cascading Style Sheets), and SMIL, the Web’s multimedia language, as well as spinning off companies such as NLNet that set up the initial Dutch Internet infrastructure, and General Design, the first Dutch Web Design company.


Please contact:
Steven Pemberton - CWI
Tel: +31 624 671 668
E-mail: steven.pemberton@cwi.nl