3. Links

In this specification, a link is a typed connection between two resources that are identified by Internationalised Resource Identifiers (IRIs) [RFC3987], and is comprised of:

o A context IRI,

o a link relation type (Section 4),

o a target IRI, and

o optionally, target attributes.

A link can be viewed as a statement of the form "{context IRI} has a {relation type} resource at {target IRI}, which has {target attributes}".

Note that in the common case, the context IRI will also be a URI [RFC3986], because many protocols (such as HTTP) do not support dereferencing IRIs. Likewise, the target IRI will be converted to a URI (see [RFC3987], Section 3.1) in serialisations that do not support IRIs (e.g., the Link header).

This specification does not place restrictions on the cardinality of links; there can be multiple links to and from a particular IRI, and multiple links of different types between two given IRIs. Likewise, the relative ordering of links in any particular serialisation, or between serialisations (e.g., the Link header and in-content links) is not specified or significant in this specification; applications that wish to consider ordering significant can do so.

Target attributes are a set of key/value pairs that describe the link or its target; for example, a media type hint. This specification does not attempt to coordinate their names or use, but does provide common target attributes for use in the Link HTTP header.

Finally, this specification does not define a general syntax for expressing links, nor does it mandate a specific context for any given link; it is expected that serialisations of links will specify both aspects. One such serialisation is communication of links through HTTP headers, specified in Section 5.