Extensible Markup Language (XML) is a mark up language that provides a format for describing structured data. This facilitates more precise declarations of content and more meaningful search results across multiple platforms. XML therefore enables a new generation of web based data viewing and manipulation applications.
Outwardly, XML looks like HTML. XML is a subset of SGML (Standard Generalized Markup
Language) that is optimized for delivery over the web. XML standards are defined by the World Wide Web
Consortium (W3C) and they ensure that structured data will be uniform and independent of application or vendors. HTML specifics how to display data in a browser while XML defines the content. XML
documents are extensible, structured and self-validating. In XML, you can define an unlimited set of
tags. XML provides a framework for tagging structured data. An XML element can declare its data
to be a retail price, book title or any other desired data element.
XML provides a means of including metadata in web documents. Metadata is information about information. The display of XML documents is typically accomplished with style sheets such as Extensible Style Language (XSL) and Cascading Style Sheets (CSS).
XML is only a specification. A document is entitled to be called an XML document only if it adheres to the rules laid down in the XML specification. XML documents are designed for use by XML processors.XML processor has a component called the XML parser that analyzes XML markup and determines the structure of the document data.