19.6.2.4 Link

The Link entity-header field provides a means for describing a relationship between two resources, generally between the requested resource and some other resource. An entity MAY include multiple Link values. Links at the metainformation level typically indicate relationships like hierarchical structure and navigation paths. The Link field is semantically equivalent to the <LINK> element in HTML.[5]

          Link           = "Link" ":" #("<" URI ">" *( ";" link-param )

          link-param     = ( ( "rel" "=" relationship )
                             | ( "rev" "=" relationship )
                             | ( "title" "=" quoted-string )
                             | ( "anchor" "=" <"> URI <"> )
                             | ( link-extension ) )

          link-extension = token [ "=" ( token | quoted-string ) ]

          relationship   = sgml-name
                         | ( <"> sgml-name *( SP sgml-name) <"> )

          sgml-name      = ALPHA *( ALPHA | DIGIT | "." | "-" )

Relationship values are case-insensitive and MAY be extended within the constraints of the sgml-name syntax. The title parameter MAY be used to label the destination of a link such that it can be used as identification within a human-readable menu. The anchor parameter MAY be used to indicate a source anchor other than the entire current resource, such as a fragment of this resource or a third resource.

Examples of usage include:

       Link: <http://www.cern.ch/TheBook/chapter2>; rel="Previous"

       Link: <mailto:timbl@w3.org>; rev="Made"; title="Tim Berners-Lee"

The first example indicates that chapter2 is previous to this resource in a logical navigation path. The second indicates that the person responsible for making the resource available is identified by the given e-mail address.