XLink
XML Linking Language,orXLink,is anXMLmarkup languageandW3Cspecification that provides methods for creating internal and external links within XML documents, and associating metadata with those links.[1]
The XLink specification
[edit]XLink 1.1 is a W3C recommendation[2]and the successor of XLink 1.0, which was also a W3C recommendation.[3] [4]
Linking with XLink
[edit]XLink defines a set ofattributesthat may be added to elements of otherXML namespaces.XLink provides two kinds of hyperlinking for use in XML documents.Simple linksconnect only two resources, similar toHTMLlinks.Extended linkscan link an arbitrary number of resources.
Simple links
[edit]Asimple linkcreates a unidirectionalhyperlinkfrom one element to another via aURI.Example:
<?xml version= "1.0"?>
<documentxmlns="http://example.org/xmlns/2002/document"xmlns:xlink="http:// w3.org/1999/xlink">
<headingid="someHeading">SomeDocument</heading>
<para>Hereis<anchorxlink:type="simple"xlink:href="#someHeading">alink</anchor>totheheader.</para>
<para>Itisananchorthatpointstotheelementwiththeid"someHeading"onthecurrentpage.</para>
</document>
Extended links
[edit]Extended linksallow multiple resources, either remote or local, to be connected by multiple arcs. Anarcis information about the origin, destination and behavior of a link between two resources. The origin and destination resources are defined by labels. By using one or more arcs, an extended link can achieve specific sets of connections between multiple resources.
For example, if all resources in an extended link were given the labelA,then an arc within that link declaringfrom= "A",to="A"
would form connections between all resources.
Extended links do not need to be contained in the same document as the elements they link to. This makes it possible to associate metadata or other supplementary information with resources without editing those resources.
XLink also supports richer information about link types and the roles of each resource in an arc.
Support for XLink
[edit]Within other specifications
[edit]SVG
[edit]Hypertext links inScalable Vector Graphicscan currently be defined as simple XLinks.[5]Theworking draftof SVG 1.2 proposes using extended XLinks as well.[6]In the SVG 2 specification, XLink was deprecated in favor of non-namespaced equivalent attributes.[7]
RDDL
[edit]TheResource Directory Description Language,an extension toXHTML Basicthat is used to describeXML Namespaces,uses simple XLinks.[8]
XBRL
[edit]TheeXtensible Business Reporting Languagehas used simple and extended XLinks since the XBRL 2.0 specification was published in 2001.[9]Most large XBRL taxonomies contain extensive linkbases. As of 2009, XBRL is probably the most extensive use of XLink in production systems.
METS
[edit]TheMetadata Encoding and Transmission Standard,supported and maintained by theLibrary of Congressfor describing file aggregations, uses simple XLinks in pointing to file locations as well as linkbases which describe relationships among external files (though these restrictto
andfrom
attributes to type IDREF instead of NMTOKEN).[10][11]
GML
[edit]Geography Markup Languageuses simple XLinks to implement referencing. In particular, GML uses xlink:href to support a graph model for geospatial information. GML's graph model is essentially the same asRDF,on which early versions of GML were based. The GML specification constrains the semantics of XLinks to be essentially the same as rdf:resource (from the RDF/XML syntax) i.e. the referent can logically be placed in-line and the data is still valid.
Implementations
[edit]Mozilla Firefox
[edit]Mozilla Firefoxhas supported simple XLinks since version 1.5, but only forSVGandMathMLdocuments. It is unsupported in other XML documents.[12]Only thexlink:href
,xlink:show
,xlink:target
andxlink:title
attributes are supported.[13]
Prince
[edit]Princesupports simple XLinks.[14]
References
[edit]- ^DeRose, Steven J. (1999-02-24),XML XLink Requirements,W3C
- ^XML Linking Language (XLink) Version 1.1,W3C, May 6, 2010
- ^XML Linking Language (XLink) Version 1.0,W3C, June 8, 2006
- ^"XML and Semantic Web W3C Standards Timeline"(PDF).
- ^Scalable Vector Graphics (SVG) 1.1 Specification: Linking,W3C, June 8, 2006
- ^Extended Links (SVG 1.2),W3C, June 8, 2006
- ^"Linking — SVG 2".w3.org.Retrieved2016-09-18.
- ^Borden, Jonathan; Bray, Tim (2002-02-18),Resource Directory Description Language (RDDL),The Open Healthcare Group, Antarcti.ca Systems
- ^Extensible Business Reporting Language (XBRL) 2.1 - XLink in XBRL,XBRL International Inc.
- ^METS: An Overview & Tutorial,Library of Congress
- ^Metadata Encoding and Transmission Standard: Primer and Reference Manual(PDF),Library of Congress, September 2007, p. 133
- ^XLink - MDC,Mozilla, archived fromthe originalon 2012-04-06,retrieved2010-02-19
- ^SVG in Firefox,Mozilla, archived fromthe originalon 2008-08-29,retrieved2010-02-19
- ^Prince: XML Input,YesLogic