XML is intended `to make it easy and straightforward to use SGML on the Web: easy to define document types, easy to author and manage SGML-defined documents, and easy to transmit and share them across the Web.'
It defines `an extremely simple dialect of SGML which is completely described in the XML Specification. The goal is to enable generic SGML to be served, received, and processed on the Web in the way that is now possible with HTML.'
`For this reason, XML has been designed for ease of implementation, and for interoperability with both SGML and HTML'
[Quotes are from the XML specification]. XML is not just for Web pages: it can be used to store any kind of structured information, and to enclose or encapsulate information in order to pass it between different computing systems which would otherwise be unable to communicate.