XML (eXtensible Markup Language) is a World Wide Web Consortium (W3C) standard, similar to HTML, for document markup. XML is based on Standard Generalized Markup Language(SGML).The first version of XML (XML 1.0) specification was published in 1998. There have been minor changes to this version and is currently in its fifth edition, but the version number remains the same. A second version of XML (XML 1.1) was published in 2004 and is currently in its third edition.
Even though there are similarities between HTML and XML, they both serve different purpose. HTML is used to display the data in a specific format while XML is used to describe the data. The tags in an XML document will only define the structure of that document and not its presentation. While HTML comes with predefined elements, XML lets the users create their own custom elements. XML specification defines only the syntax of the elements and gives the users the flexibility to create their own tags based on their specific needs. So for example, an XML document for a movie will have tag names like <title>, <releasedate>, <language>, <actors> etc. XML files typically use the filename extension .xml
The advantages of XML are its simplicity, extensibility, flexibility and portability. It is a meta markup language which means you can develop other languages with XML. XHTML is an example. XML is now widely used in web publishing, for database development and to share data across heterogeneous hardware and software systems.
This is a beginner's guide to XML.