Among web developers, anticipation is mounting for HTML 5, the overhaul of the web markup language currently under way at the Worldwide Web Consortium (W3C). For many, the revamping is long overdue. HTML hasn't had a proper upgrade in more than a decade. In fact, the last markup language to win W3C Recommendation status, the final stage of the web standards process, was XHTML 1.1 in 2001.

In the intervening years, web developers have grown increasingly restless. Many claim the HTML and XHTML standards have become outdated, and that their document-centric focus does not adequately address the needs of modern Web applications.



Modernising HTML for the rich web

Rich applications and HTML have not always been a natural fit. The father of the web, Tim Berners-Lee, envisioned HTML as "a simple markup language used to create hypertext documents that are platform independent." With the advent of XHTML, the pure XML formulation of the language, the W3C maintained this focus on web pages as documents, with the proposed XHTML standards emphasising such issues as document structure, compatibility with XML tools, and Berners-Lee's vision of the Semantic Web.

This frustrated many developers who saw greater potential in the web as an application platform. In 2004, representatives of Apple, the Mozilla Foundation, and Opera Software founded the Web Hypertext Application Technology Working Group (WHATWG), an independent web standards consortium. Working outside the W3C, WHATWG began a parallel effort to revamp HTML for a more application-centric view of the web.


That's not to say the concept of a pure-XML web markup language is dead. Although HTML has retaken the lead role in the standards effort, an XML formulation of HTML 5, to be known as XHTML 5, is being developed at the same time. The difference is that while XHTML 5 will be available for those who have already made the switch, developers will no longer be required to observe the rigorous syntax of XHTML to take advantage of web markup's latest features.

HTML 5: Markup gets a makeover

Be that as it may, HTML 5 has inherited many additions originally proposed for XHTML 2, including a number of features designed to improve document structure. For example, new HTML tags such as header, footer, dialog, aside, and figure allow content authors to specify common document elements in a consistent way. Previously, developers had to mark such elements using div tags with custom class attributes, an arbitrary method that made HTML documents difficult to parse.

HTML 5 also continues the effort to separate web content from presentation. Developers might be surprised to see the b and i elements available in the new standard, for example, but these elements are now used to offset portions of text in generic ways, without implying any specific typographic treatment. Where the i element once implied italic type, for example, in HTML 5 it merely means "a span of text in an alternate voice or mood." Similarly, the b element does not imply specifically boldfaced text, but text that is stylistically offset without having any additional importance.

By comparison, the u tag, which referred specifically to underlined text, has been dropped from HTML 5, along with other presentation specific elements, including font, center and strike. Such stylistic attributes are now considered the exclusive domain of CSS.

The new standard introduces additional data types for form input elements, including dates, URLs and email addresses. Still other elements improve support for non-Latin character sets, including tags for specifying the "ruby text" that appears in some Asian languages. HTML 5 also introduces the concept of microdata, a method of annotating HTML content with machine readable tags, making it easier to process for the Semantic Web. Together, these structural enhancements allow content authors to build cleaner, more manageable web pages that play nicely with search engines, screen readers and other automated content parsers.