The XPointer does not specify the document. A URI does.
XPointers can be used as fragment identifiers
in a URI after a #
For example,
http://www.w3.org/TR/1998/REC-xml-19980210.xml#xpointer(id("ebnf"))
http://www.w3.org/TR/1998/REC-xml-19980210.xml#xpointer(descendant::language[position()=2])
http://www.w3.org/TR/1998/REC-xml-19980210.xml#ebnf
http://www.w3.org/TR/1998/REC-xml-19980210.xml#xpointer(/child::spec/child::body/child::*/child::language[position()=2])
http://www.w3.org/TR/1998/REC-xml-19980210.xml#element(/1/14/2)
http://www.w3.org/TR/1998/REC-xml-19980210.xml#xpointer(id("ebnf"))xpointer(id("EBNF"))