Overview Extensible Markup Language (XML)
Extensible Markup Language (XML) is a not a language in the true sense of the word, Wikipedia describe XML, “XML is a way of describing data and an XML file can contain the data too, as in a database.” (http://en.wikipedia.org/wiki/Xml)Governed by the World Wide Web Consortium XML concept was first introduced in 1996, chaired by Jon Bosak of Sun Microsystems (1996), but it was not until February 10th 1998 that XML was finally formed and released as a W3C recommendation standard, version 1.0. (http://www.w3.org)
HTML tags are always pre-defined, you may have seen a set <b>bold</b>, but XML however does not have pre-defined tags. Users can define their own tags, making the possibilities almost endless.
Although above a comparison is being made to HTML It is important not to compare XML with HTML as each was intended to do different things. HTML concentrates on how data is displayed or looks on a page, where XML is used to describe data and force validation.
A XML document can be valid against a schema, and it must obey the rules set in the chosen schema if one is applied. Document Type Definition (DTD) is one of several XML schema languages available, another alternative would be XML Schema Definition (XSD). A DTD can define elements and attributes structures, it could also be used describe how character data is understood or a date and number field datatype is validated.
XML documents must be ‘Well Formed’ meaning the correct XML syntax must be used.
Opening a standard XML document in a browser will not instruct the browser how to present that information on screen. To style and layout to a XML document a Cascading Style Sheet (CSS) could be used.
However, W3C’s recommend a dynamic Extensible Stylesheet Language (XSL) to format XML document, Like CSS it can style data, but unlike CSS, it contains dynamic elements to transform documents, navigation and format them, e.g. Extensible Stylesheet Language Transformations (XSLT) using XPath can navigate elements in the XML document, something that’s just not possible with CSS.
This page was created on:
Last modified: 12/15/2006
