id()

• The id() function selects the element in the document that has an ID type attribute with a specified value.

• For example, consider the URI http://www.theharolds.com/genealogy.xml#xpointer(id("p12")). If you look back at Listing 17-1, you find this element:

  <PERSON ID="p12" FATHER="p2" MOTHER="p1">
    <NAME>Honore Bellau</NAME>
  </PERSON>
  

• Since ID pointers are so common and so useful, there's also a shortcut for this. If all you want to do is point to a particular element with a particular ID, you can skip all the xpointer(id("")) fru-fru and just use the bare ID after the # like this:

  http://www.theharolds.com/genealogy.xml#p12