XPointer is a system for addressing components of XML based internet media.

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. XPointer Framework is a recommendation since March 2003.^[1]

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 royalty-free technology patent held by Sun Microsystems.^[2]

[edit] 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:

 <foobar id="foo">   <bar/>   <baz>     <bom a="1"/>   </baz>   <bom a="2"/> </foobar> 

results as the following examples:

  xpointer(id("foo")) => foobar  xpointer(/foobar/1) => bar  xpointer(//bom) => bom (a=1), bom (a=2)  element(/1/2/1) => bom (a=1) (/1 descend into first element (foobar),                                /2 descend into second child element (baz),                                /1 select first child element (bom)) 

[edit] See also

• Fragment identifier
• XML
• HTML
• HyTime
• Text Encoding Initiative Guidelines

[edit] References

1. ^ "XPointer Framework". http://www.w3.org/TR/2003/REC-xptr-framework-20030325/. Retrieved April 13 2009. 
2. ^ XPointer royalty-free patent statement

[edit] External links

• XPointer Framework
• Positional element addressing
• Namespacing
• Path based addressing
• XPointer patent terms and conditions
• Open source implementation (CognitiveWeb)
• GPL License .NET implementation (XInclude.NET)