View source for rel-enclosure

{{DISPLAYTITLE:rel="enclosure"}}
{{DraftSpecification}}

rel-enclosure is a simple, open, format for indicating files to cache which is  embeddable in (X)HTML, Atom, RSS, and arbitrary XML. relEnclosure is an [[elemental-microformat|elemental microformat]], one of several [[microformats|microformat]] open standards.
__TOC__
== Draft Specification 2005-06-21 ==
=== Author ===
[http://epeus.blogspot.com Kevin Marks], [http://technorati.com Technorati, Inc.]

=== Copyright ===
{{MicroFormatCopyrightStatement2004}}

=== Patents ===
{{MicroFormatPatentStatement}}

== Abstract ==

relEnclosure is one of several microformats.  By adding <code>rel="enclosure"</code> to a hyperlink, a page indicates that the destination of that hyperlink is intended to be downloaded and cached. E.g. with the following hyperlink:

<pre><nowiki>
<a href="http://homepage.mac.com/kevinmarks/wwdc2005.mov" rel="enclosure">WWDC 2005 Keynote with chapters</a>
</nowiki></pre>

the author indicates that the movie should be downloaded.

== Multiple Enclosures ==
Multiple such rel="enclosure" hyperlinks indicate that several media items should be downloaded.

'''Question:''' What if there are several alternative formats, such as high- and low-bandwidth recordings? Since <link rel="alternate" href="..."> is already defined in XHTML for that purpose, so how should it interact with this new rel tag?

'''Response:''' rel="alternate" is defined in the HTML spec:

<blockquote>Designates substitute versions for the document in which the link occurs.</blockquote>

In the case of enclosure links "alternate" is not suited, because the media file is not a substitute version of the document in which the link occurs - it is a substitute version of another link on the document in which the link occurs.

'''Proposal:''' Multiple instances of the same enclosure (i.e. same video with different formats, size/resolution, bitrates, etc) could be grouped in a class="enclosure" block with multiple rel="enclosure" links. This would be analogous to <media:group> in [http://search.yahoo.com/mrss MRSS]

===reply===
*"In the case of enclosure links "alternate" is not suited, because the media file is not a substitute version of the document in which the link occurs "
**That's not necessarily the case; the linked file may be an audio reading of the text on the page, for instance. [[User:AndyMabbett|Andy Mabbett]] 02:37, 5 Oct 2007 (PDT)

== XMDP profile ==
<pre><nowiki>
<dl class="profile">
 <dt id="rel">rel</dt>
 <dd><p>
   <a rel="help" href="http://www.w3.org/TR/html401/struct/links.html#adef-rel">
     HTML4 definition of the 'rel' attribute.</a>  
   Here is an additional value.</p>
  <dl>
   <dt id="enclosure"> enclosure </dt>
   <dd>Indicates that the referred resource is intended to be downloaded and cached</dd>
  </dl>
 </dd>
</dl>
</nowiki></pre>

==Examples in the Wild==
This section is '''informative'''.

The following sites have implemented rel-enclosure, and thus are a great place to start for anyone looking for examples "in the wild" to try parsing, indexing, organizing etc. If your site is marked up with rel-enclosure, feel free to add it to the '''top''' of this list. Once the list grows too big, we'll make a separate wiki page.
* [http://huffduffer.com/ Huffduffer] uses rel-enclosure on links to audio files marked "download".

== Implementations ==
This section is '''informative'''.

The following implementations have been developed which either generate or parse rel-enclosure links. If you have a rel-enclosure implementation, feel free to add it to the top of this list. Once the list grows too big, we'll make a separate wiki page.

* [http://www.feedburner.com FeedBurner]: the [http://forums.feedburner.com/viewtopic.php?t=20 SmartCast] service looks for the rel="enclosure" microformat and converts it to an enclosure in the feed.
* [http://odeo.com ODEO] [http://odeo.com/blog/2005/07/adding-microformats-to-odeo.html publishes] rel-enclosure links for user podcast MP3s.
* [http://joshkinberg.com/popupmaker/ Video Pop-Up Link Maker]: generates code for rel-enclosure links for videobloggers. Also generates Javascript to launch a pop-up window with the video embedded. (Also available at [http://embedthevideo.com/ embedthevideo.com])

== References ==
=== Normative References ===
* [http://gmpg.org/xmdp/ XMDP]

=== Informative References ===
* [http://www.ietf.org/rfc/rfc4287.txt The Atom Syndication Format]: 
** 4.2.7.2  The "rel" Attribute
   4.  The value "enclosure" signifies that the IRI in the value of the
       href attribute identifies a related resource which is potentially
       large in size and might require special handling.  For atom:link
       elements with rel="enclosure", the length attribute SHOULD be
       provided.


==See also==

* [[rel-enclosure-brainstorming]]
{{rel-related-pages}}

[[Category:Draft Specifications]]
[[Category:rel-enclosure]]