A link relation is a descriptive attribute attached to a hyperlink in order to define the type of the link, or the relationship between the source and destination resources. The attribute can be used by automated systems, or can be presented to a user in a different way.
In HTML these are designated with the rel attribute on link, a, or area elements. Example uses include the standard way of referencing CSS, <link rel="stylesheet" href="example.css" />, which indicates that the external resource linked to with the href attribute is a stylesheet, so a web browser will generally fetch this file to render the page. Another example is rel="shortcut icon" for the popular favicon icon.[1][2]
Link relations are used in some microformats (e.g. rel="tag" for tagging), in XHTML Friends Network (XFN), and in the Atom standard, in XLink, as well as in HTML. Standardized link relations are one of the foundations of HATEOAS as they allow the user agent to understand the meaning of the available state transitions in a REST system.
The Internet Engineering Task Force (IETF) has a registry of standardized link relations,[3] and a procedure for extending it defined in RFC 5988. HTML5 also defines valid link relations.[4]
In HTML4, the rev attribute of a link is also defined, which defines the reversed relationship between the resources. The attribute is removed in HTML5.
Semantic Web implementationedit
The RDF typed links are fundamental in LOD datasets for identifying the relationship (predicate) type of RDF triples, contributing to the automatic processability of machine-readable statements of the Giant Global Graph on the Semantic Web. The typed links in RDF are expressed as the value of the rdf:type property, defining the relationship type using well-established controlled vocabulary terms or definitions from LOD datasets such as
link, relation, link, relation, descriptive, attribute, attached, hyperlink, order, define, type, link, relationship, between, source, destination, resources, attribute, used, automated, systems, presented, user, different, html, these, designated, with, attri. A link relation is a descriptive attribute attached to a hyperlink in order to define the type of the link or the relationship between the source and destination resources The attribute can be used by automated systems or can be presented to a user in a different way In HTML these are designated with the rel attribute on link a or area elements Example uses include the standard way of referencing CSS lt link rel stylesheet href example css gt which indicates that the external resource linked to with the href attribute is a stylesheet so a web browser will generally fetch this file to render the page Another example is rel shortcut icon for the popular favicon icon 1 2 Link relations are used in some microformats e g rel tag for tagging in XHTML Friends Network XFN and in the Atom standard in XLink as well as in HTML Standardized link relations are one of the foundations of HATEOAS as they allow the user agent to understand the meaning of the available state transitions in a REST system The Internet Engineering Task Force IETF has a registry of standardized link relations 3 and a procedure for extending it defined in RFC 5988 HTML5 also defines valid link relations 4 In HTML4 the rev attribute of a link is also defined which defines the reversed relationship between the resources The attribute is removed in HTML5 Semantic Web implementation editThe RDF typed links are fundamental in LOD datasets for identifying the relationship predicate type of RDF triples contributing to the automatic processability of machine readable statements of the Giant Global Graph on the Semantic Web The typed links in RDF are expressed as the value of the rdf type property defining the relationship type using well established controlled vocabulary terms or definitions from LOD datasets such as lt rdf type rdf resource http schema org Person gt References edit Dubost Karl October 2005 Web site meta data profile favicon World Wide Web Consortium Retrieved 23 February 2011 Dubost Karl 24 October 2005 How to Add a Favicon to your Site World Wide Web Consortium Retrieved 25 February 2011 IANA link relations registry HTML Living Standard 4 12 4 Link types Web Hypertext Application Technology Working GroupExternal links editrel values defined in HTML 4 rel values to be defined in HTML5 rel values which are defined in some specification WHATWG blog entry on link relations nbsp This World Wide Web related article is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Link relation amp oldid 1216055884, wikipedia, wiki, book, books, library,
