[Where does one read about XPointer, and what does it do in relation to XML ]?
XPointer is an adjunct to Uniform Resource Identifiers (URIs) to allow XML resources to be linked into. Unlike HTML, it can be used to get to any arbitrary region inside an XML file.
See also XLink.
Both the XLink and the XPointer specifications are currently on the W3C (http://www.w3c.org/ ) Recommendation track, which makes them loosely considered a standard already. Both are in the Candidate Recommendation phase.