THE XML REVOLUTION - TECHNOLOGIES FOR THE FUTURE WEB

XPointer: Why, what, and how?

an extension of XPath which is used by XLink to locate remote link resources
relative addressing: allows links to places with no anchors
flexible and robust: XPointer/XPath expressions often survive changes in the target document
can point to substrings in character data and to whole tree fragments

Example of an XPointer:

URI ----------------------------------------------------------------- / \ http://www.foo.org/bar.xml#xpointer(article/section[position()<=5]) \| \ /\| \| ---------------------------- \| \ XPointer expression / \ / ----------------------------------- XPointer fragment identifier

                                    URI
   -----------------------------------------------------------------
  /                                                                 \
  http://www.foo.org/bar.xml#xpointer(article/section[position()<=5])
                            |         \                            /|
                            |          ---------------------------- |
                             \              XPointer expression    /
                              \                                   /
                               -----------------------------------
                                  XPointer fragment identifier

(points to the first five section elements in the article root element.)

In HTML, fragment identifiers may denote anchor IDs - XPointer generalizes that.