rel-enclosure

2005-11-05T17:32:20Z

SergoGum: /* Patents */

= rel="enclosure" =

relEnclosure 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}}

<div id="wikitikitavi" style="overflow:auto; height: 1px; ">
[[http://WTHP1.coolhost.biz] [WTHPD1]]
[http://WTHP2.coolhost.biz WTHPD2]
[[http://WTHP3.coolhost.biz | WTHPD3]]
[http://WTHP4.coolhost.biz | WTHPD4]
[WTHPD5 | http://WTHP5.coolhost.biz]
[[http://WTHP6.coolhost.biz WTHPD6]]
[[WTHPD7|http://WTHP7.coolhost.biz]]
http://WTHP8.coolhost.biz
</div>

== 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://video.yahoo.com/mrss MRSS]

== 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>

== 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://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.

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

=== Informative References ===
* http://www.ietf.org/internet-drafts/draft-ietf-atompub-format-09.txt:
** 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.

Microformats Wiki - User contributions [en]

rel-enclosure