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RSS FAQs - Atom Syndiation Format RFC4287 Reference Document

By: M. Nottingham, Ed. & R. Sayre, Ed.

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      http://www.example.org/thing
      http://www.example.org/Thing
      http://www.EXAMPLE.org/thing
      HTTP://www.example.org/thing

   Likewise, these are three distinct identifiers, because IRI
   %-escaping is significant for the purposes of comparison:

      http://www.example.com/~bob
      http://www.example.com/%7ebob
      http://www.example.com/%7Ebob

4.2.7.  The "atom:link" Element

   The "atom:link" element defines a reference from an entry or feed to
   a Web resource.  This specification assigns no meaning to the content
   (if any) of this element.

   atomLink =
      element atom:link {
         atomCommonAttributes,
         attribute href { atomUri },
         attribute rel { atomNCName | atomUri }?,
         attribute type { atomMediaType }?,
         attribute hreflang { atomLanguageTag }?,
         attribute title { text }?,
         attribute length { text }?,
         undefinedContent
      }

4.2.7.1.  The "href" Attribute

   The "href" attribute contains the link's IRI. atom:link elements MUST
   have an href attribute, whose value MUST be a IRI reference
   [RFC3987].

4.2.7.2.  The "rel" Attribute

   atom:link elements MAY have a "rel" attribute that indicates the link
   relation type.  If the "rel" attribute is not present, the link
   element MUST be interpreted as if the link relation type is
   "alternate".

   The value of "rel" MUST be a string that is non-empty and matches
   either the "isegment-nz-nc" or the "IRI" production in [RFC3987].
   Note that use of a relative reference other than a simple name is not
   allowed.  If a name is given, implementations MUST consider the link
   relation type equivalent to the same name registered within the IANA

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   Registry of Link Relations (Section 7), and thus to the IRI that
   would be obtained by appending the value of the rel attribute to the
   string "http://www.iana.org/assignments/relation/".  The value of
   "rel" describes the meaning of the link, but does not impose any
   behavioral requirements on Atom Processors.

   This document defines five initial values for the Registry of Link
   Relations:

   1.  The value "alternate" signifies that the IRI in the value of the
       href attribute identifies an alternate version of the resource
       described by the containing element.

   2.  The value "related" signifies that the IRI in the value of the
       href attribute identifies a resource related to the resource
       described by the containing element.  For example, the feed for a
       site that discusses the performance of the search engine at
       "http://search.example.com" might contain, as a child of
       atom:feed:

       <link rel="related" href="http://search.example.com/"/>

       An identical link might appear as a child of any atom:entry whose
       content contains a discussion of that same search engine.

   3.  The value "self" signifies that the IRI in the value of the href
       attribute identifies a resource equivalent to the containing
       element.

   4.  The value "enclosure" signifies that the IRI in the value of the
       href attribute identifies a related resource that is potentially
       large in size and might require special handling.  For atom:link
       elements with rel="enclosure", the length attribute SHOULD be
       provided.

   5.  The value "via" signifies that the IRI in the value of the href
       attribute identifies a resource that is the source of the
       information provided in the containing element.

4.2.7.3.  The "type" Attribute

   On the link element, the "type" attribute's value is an advisory
   media type: it is a hint about the type of the representation that is
   expected to be returned when the value of the href attribute is
   dereferenced.  Note that the type attribute does not override the
   actual media type returned with the representation.  Link elements
   MAY have a type attribute, whose value MUST conform to the syntax of
   a MIME media type [MIMEREG].

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