Learn The Extensible Markup Language (XML)

The Extensible Markup Language (short XML) is a computer language. It is a markup language like HTML but is extensible. It's created by the World Wide Web Consortium (W3C). XML defines rules for the construction of a document. XML adds context to the information in a document. It does not say how this should be displayed.

Some programs get information out of an XML-document. To do that, they need an API. There are many APIs for XML.

You can write a description of an XML document in a way that is useful for programmers. There are several languages for this; the best known is called DTD.
From Wikipedia, the free encyclopedia

XML OfficialWebsite

Learn XML
http://www.w3schools.com/xml/default.ASP
http://www.tizag.com/xmlTutorial/
http://www.learn-xml-tutorial.com/
http://www.xmlfiles.com/xml/