XPointer is a system for addressing components of XML based internet media.
At the present time (late 2002), XPointer is divided among four specifications: a "framework" which forms the basis for identifying XML fragments, a positional element addressing scheme, a scheme for namespaces, and a scheme for XPath-based addressing.
The XPointer language is designed to address structural aspects of XML, including text content and other information objects created as a result of parsing the document. Thus, it could be used to point to a section of a document highlighted by a user through a mouse drag action.
XPointer is covered by a technology patent held by Sun Microsystems.
Positional Element Addressing
The element() scheme introduces positional addressing of child elements. This is similar to a simple XPath address, but subsequent steps can only be numbers representing the position of a descendant relative to its branch on the tree.
For instance, given the following fragment:
<bar/>
<baz>
<bom a="1"/>
</baz>
<bom a="2"/>
</foobar>
results as the following examples:
xpointer(/foobar/1) => bar
xpointer(//bom) => bom (a=1), bom (a=2)
xpointer(/1/2/1) => bom (a=1) (/1 descend into first element (foobar), descend into second child element (baz), select first child element (bom))
Reference:
http://en.wikipedia.org/wiki/Xpointer
