XML is a W3C-recommended general-purpose markup language that supports a wide variety of applications, and is extensible. XML is a simplified subset of Standard Generalized Markup Language (SGML). DITA is a "dialect" of XML.
The following figure shows a simple, annotated XML file.
The following figure shows the XML object model for the simple XML file.
The following figure shows a simplified tree structure model for a typical DITA project.