Technologies for the Near Future

XML

Read all about XML and the W3C's XML Activity at the W3C web site.

What is it?

XML is a "meta-language": a language that is used to write other languages. It looks a little like HTML, but in fact HTML is written in SGML, a related meta-language. XML is a simplified version of SGML, which means that languages written in XML can be understood with less processing than languages written in SGML. One use of XML that the W3C has been working on is to rewrite HTML in XML. The first version of this new language, XHTML, is now a W3C Recommendation. It looks a lot like old-fashioned HTML, and can actually be used in standard, old-fashioned HTML browsers such as Explorer, Lynx, Mosaic, Netscape and Opera.

How is it made?

There are two parts to using XML. The first is to define a language. For example, XHTML uses a Document Type Definition (DTD) to describe the rules for XHTML elements (tags). Then an actual XHTML document is written using those tags according to the rules in the DTD.

Who is using it?

XML is being used for many different purposes. Many new Web languages (including XHTML and the other languages discussed in this paper) are written in XML. Databases are being encoded in XML. WML, the markup language developed by the WAP forum for mobile telephones, is written in XML (and work is underway to unify it with XHTML). It can be used to encode music, mathematics, graphics, books, and abstract, machine-readable data, as well as word-processor documents, spreadsheets and Web pages. The OASIS group are tracking XML use and development in various subject areas

What does it look like?

This web page is written in XHTML (which is one application of XML). You can read the source of the page, and if you are familiar with HTML you will notice there is very little difference.

Where is it going?

Everywhere. But it is also being extended. Using the XML namespaces Recommendation it is possible to include multiple XML languages in a single document. Current work is being done to provide a means of adding links to any XML language, to provide a Document Object Model (DOM) that can be used by interactive scripts to provide dynamic changes, to provide a schema language which will enable better validation and machine understanding of XML data, and to develop means of handling small fragments of XML, stylesheets, transformations between different XML languages, and other useful tools.

This page was produced by Charles McCathieNevile of W3C as part of a presentation for online@RMIT. All responsibility for errors rests with the author.