Java API - Class XPointer
http://www-4.ibm.com/software/developer/education/tutorial-prog/xml4j/TXapiDocs/com/ibm/xml/xpointer
Details of the XPointer class for Java 2.0.9 compatibility API.
XML Pointer Language (XPointer)
A specification of constructs that support addressing into the internal structures of XML documents. It provides for specific reference to elements, character strings, and other parts of XML documents, whether or not they bear an explicit ID attribute. (W3C Candidate Recommendation 11 September 2001)