XPointer
XPointer is a system for addressing components of XML-based Internet media. It is divided among four specifications: a "framework" that forms the basis for identifying XML fragments, a positional element addressing scheme, a scheme for namespaces, and a scheme for XPath-based addressing. XPointer Framework is a W3C recommendation since March 2003. 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. During development, and until 2016, XPointer was covered by a royalty-free technology patent held by Sun Microsystems. Positional Element Addressing. The codice_1 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: <foobar id="foo"> </foobar> results as the following examples: