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URL:
http://www.w3.org/XML/
The eXtensible Markup Language (XML) is an
application profile or restricted form of SGML, and has become a very widely
used system for defining data formats. Its goal is to enable generic SGML to be
served, received, and processed on the Web in the way that is now possible with
HTML. XML has been designed for ease of implementation and for interoperability
with both SGML and HTML.
It is called extensible because it is not a fixed
format like HTML (a single, predefined markup language). Instead, XML is
actually a `meta-language' - a language for describing other languages - that
allows for the design of customized markup languages for limitless different
types of documents.
XML is defined by W3C at W3C: eXtensible Markup
Language (XML). The base specifications are XML 1.0, and Namespaces.
XML describes a class of data objects called XML
documents and partially describes the behavior of computer programs which
process them. By construction, XML documents are conforming SGML documents. XML
documents are made up of storage units called entities, which contain either
parsed or unparsed data. Parsed data is made up of characters, some of which
form character data, and some of which form markup. Markup encodes a
description of the document's storage layout and logical structure. XML
provides a mechanism to impose constraints on the storage layout and logical
structure.
XML provides a very rich system to define complex
documents and data structures such as invoices, molecular data, news feeds,
glossaries, inventory descriptions, real estate properties, etc. As long as a
programmer has the XML definition for a collection of data (often called a
"schema") then they can create a program to reliably process any data
formatted according to those rules.
A number of technologies and initiatives are being
created around or using XML, some of them include; XHTML, CSS, XSL,
DOM, SOAP, UDDI, WSDL, ebXML, and BizTalk.
Keywords:
Widespread usage
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eXtensible Markup Language (XML)
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