| home / experts / xml / column73 |
|
|
In this installment we will extend our XMLMap with XML standards for documents, particularly those concerned with presenting information to users. While the main difference between XML and HTML is that XML contains no presentation information, one of the first applications of XML was in the presentation field: Reformulating HTML in XML as XHTML.
More presentation-related XML standards followed. While a fair number of XML vocabularies were concerned with reinventing Web formats for HTML, forms and frames; the degrees of freedom inherent to XML were used to move into other presentation domains, namely voice and telecommunications.
HTML accumulated quite a bit of excess baggage on its way to version 4.0. Many features were hastily added to cover everything from better styling of documents to more dynamic pages. Lenient formatting rules and proprietary browser implementations added to the decline of interoperability, creating the challenges of Web publishing as we know it today.
XHTML version 1.0 was created to address that problem, systematically pushing styling information into style sheets, and inheriting the strict rules for well-formedness and validation from XML. Dynamic document manipulation was standardized with the Document Object Model and ECMAScript. A transitional version of XHTML was derived from the strict form, still including the most common style-related tags in order to ease transition to XHTML. A third DTD for framesets was also defined.
With the advent of more diverse computing devices such as PDAs and mobile phones various XML dialects were invented for different levels of UI capabilities, such as Wireless Markup Language (WML) for mobile phones. The proliferation of such vocabularies meant re-inventing the wheel and complicating cross-platform publishing, so version 1.1 of XHTML was modularized to accommodate a wider range of display devices and thereby hopefully putting an end to any effort to create yet another presentation format.
Recently XHTML 2.0 was drafted, moving further away from its HTML heritage and more in line with other XML document formats, such as DocBook for technical documentation, and XLink for linking documents.
HTML frames were a controversial invention straight from the beginning. They allow for combining content from different pages into one view, but created usability problems for hyperlink navigation and URL identification. XFrames try to address these problems without sacrificing their advantages. HTML forms were also reformulated in XML, leading to the XForms specification. Adoption of these standards in browsers is probably a long time away, but they can be used on the server side today and transformed with XSLT before delivery.
Let's go beyond text with graphics and voice...
Produced by Michael Claßen
| ||||||||||||||||||||
URL: http://www.webreference.com/xml/column73/index.html
Created: Jan 20, 2003
Revised: Jan 20, 2003
