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.