XPointer is a system for addressing components of XML based internet media.
XPointer is divided among four specifications: a "framework" which forms the basis for identifying XML fragments, a positional element addressing scheme, a scheme for namespaces, and a scheme for XPath-based addressing. XPointer Framework is a recommendation since March 2003.
The XPointer language is designed to address structural aspects of XML, including text content and other information objects created as a result of parsing the document. Thus, it could be used to point to a section of a document highlighted by a user through a mouse drag action.
XPointer is covered by a royalty-free technology patent held by Sun Microsystems.
Read more about XPointer: Positional Element Addressing