View source for XPointer

{{Short description|System for addressing components of XML-based Internet media}}
{{Infobox technology standard
| title             = XPointer
| long_name         = XPointer Framework
| native_name       = XPointer Framework
| native_name_lang  = en
| status            = W3C Recommendation
| year_started      = {{Start date and age|1997}}
| first_published   = {{Start date and age|1997|04|06}}<ref name="xpointer-history">{{Cite web|url=https://www.w3.org/standards/history/xptr-framework|title=XPointer Framework Publication History - W3C|website=W3C|date=n.d.|access-date=2021-04-08}}</ref><ref name="xpointer-first-pub-draft">{{Cite web|url=https://www.w3.org/TR/WD-xml-link-970406|title=Extensible Markup Language (XML): Part 2. Linking Version 1.0|date=1997-04-06|access-date=2021-04-08|website=W3C|collaboration=W3C SGML Activity|editor-first1=Tim|editor-last1=Bray|editor-first2=Steve|editor-last2=DeRose}}</ref>
| version           = XPointer Framework Recommendation<ref name="W3C-xptr-framework">{{cite web|title=XPointer Framework|url=http://www.w3.org/TR/2003/REC-xptr-framework-20030325/|publication-date=2003-03-25|access-date=2021-04-08|publisher=W3C|website=W3C|collaboration=W3C XML Linking Working Group|editor-first1=Paul|editor-last1=Grosso|editor-first2=Eve|editor-last2=Maler|editor-first3=Jonathan|editor-last3=Marsh|editor-first4=Norman|editor-last4=Walsh}}</ref>
| version_date      = {{Start date and age|2003|03|25}}<ref name="W3C-xptr-framework" />
| organization      = [[World Wide Web Consortium|W3C]]
| committee         = W3C XML Linking Working Group<ref name="working-group">{{Cite web|url=https://www.w3.org/XML/Linking|archive-url=https://web.archive.org/web/20210325053819/https://www.w3.org/XML/Linking|archive-date=2021-03-25|title=W3C XML Pointer, XML Base and XML Linking|website=W3C|date=2000|access-date=2021-04-08}}</ref>
| editors           = {{Plainlist|
* Paul Grosso
* Eve Maler
* Jonathan Marsh
* Norman Walsh
}}<ref name="W3C-xptr-framework" />
| authors           = 
| base_standards    = [[XML]], [[XPath]]
| related_standards = 
| abbreviation      =
| domain            = 
| license           = 
| website           = {{URL|https://www.w3.org/TR/xptr-framework/}}
}}

'''XPointer''' is a system for addressing components of [[XML]]-based [[Internet]] media. It is divided among four specifications: a "[[Software framework|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 [[World Wide Web Consortium|W3C]] recommendation since March 2003.<ref name="W3C-xptr-framework" /><ref name="timelinehistory">{{cite web|url=http://www.dblab.ntua.gr/~bikakis/XML%20and%20Semantic%20Web%20W3C%20Standards%20Timeline-History.pdf|url-status=dead|archive-url=https://web.archive.org/web/20191026052918/http://www.dblab.ntua.gr/~bikakis/XML%20and%20Semantic%20Web%20W3C%20Standards%20Timeline-History.pdf|archive-format=PDF|archive-date=2019-10-26|access-date=2021-04-08|title=The XML and Semantic Web Worlds: Technologies, Interoperability and Integration. A survey of the State of the Art|author1=Bikakis N.|author2=Tsinaraki C.|author3=Gioldasis N.|author4=Stavrakantonakis I.|author5=Christodoulakis S.}}</ref>

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]].<ref name="patents">{{cite web|url=http://www.w3.org/2002/06/xptr_IPR_summary.html|title=XPointer Patent Statements|website=www.w3.org|date=2002-06-10|access-date=2021-04-08|author-first=Ron|author-last=Daniel}}</ref>

== Positional element addressing ==
The <code>element()</code> scheme<ref name="xpointer-element-scheme">{{Cite web|url=https://www.w3.org/TR/xptr-element/|title=XPointer element() Scheme|publication-date=2003-03-23|access-date=2021-04-08|collaboration=W3C XML Linking Working Group|website=W3C|publisher=W3C|editor-first1=Paul|editor-last1=Grosso|editor-first2=Eve|editor-last2=Maler|editor-first3=Jonathan|editor-last3=Marsh|editor-first4=Norman|editor-last4=Walsh}}</ref> 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:

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

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))

== See also ==
* [[URI fragment]]
* [[HTML]]
* [[HyTime]]
* [[Text Encoding Initiative|Text Encoding Initiative Guidelines]]
* [[XML]]

== References ==
{{reflist}}

== External links ==
* [http://www.w3.org/TR/xptr-framework/ XPointer Framework]
* [http://www.w3.org/TR/xptr-xmlns/ Namespacing]
* [http://www.w3.org/TR/xptr-xpointer/ Path based addressing]
* [http://lists.w3.org/Archives/Public/www-xml-linking-comments/2000OctDec/0092.html XPointer patent terms and conditions]
* [https://sourceforge.net/projects/cweb Open source implementation (CognitiveWeb)]
* [https://mvp-xml.sourceforge.net/xinclude/ GPL License .NET implementation (XInclude.NET)] {{Webarchive|url=https://web.archive.org/web/20150618032805/http://mvp-xml.sourceforge.net/xinclude/ |date=2015-06-18 }}
* ''[https://patents.google.com/patent/US5659729A/en Method and system for implementing hypertext scroll attributes]'' on Google Patents, expired 2016-02-01

{{W3C Standards}}
{{Authority control}}
{{DEFAULTSORT:Xpointer}}
[[Category:World Wide Web Consortium standards]]
[[Category:XML data access]]