W3C home > Mailing lists > Public > uri@w3.org > September 2001

RE: Excess URI schemes considered harmful

From: Rob Lanphier <robla@real.com>
Date: Wed, 26 Sep 2001 00:18:30 -0700 (PDT)
To: Harald Tveit Alvestrand <harald@alvestrand.no>
cc: Eastlake III Donald-LDE008 <Donald.Eastlake@motorola.com>, <uri@w3.org>, Dan Connolly <connolly@w3.org>, Al Gilman <asgilman@iamdigex.net>, Tim Berners-Lee <timbl@w3.org>, Larry Masinter <LMM@acm.org>, Dan Zigmond <djz@corp.webtv.net>, Rich Petke <rpetke@wcom.net>
Message-ID: <Pine.LNX.4.33.0109252359270.11712-100000@mmmm.robla.org>
On Tue, 25 Sep 2001, Harald Tveit Alvestrand wrote:
> I have trouble imagining the case where you would want to use [a URI
>representation of a media type]

In SMIL 2.0, one can use the "systemComponent" attribute to query a media
player for a particular capability.  systemComponent takes a URI as a
value.

An example use:
<switch>
  <seq systemComponent="ContentType:image/png">
    <img src="slide1.png" dur="5s"/>
    <img src="slide2.png" dur="5s"/>
    <img src="slide3.png" dur="5s"/>
    <img src="slide4.png" dur="5s"/>
  </seq>
  <img src="sorry.jpg"/>
</switch>

More details can be found in the specification:
http://www.w3.org/TR/smil20/smil-content.html#adef-systemComponent

If the "image/png" media type is supported, the sequence of images should
be played.  Otherwise, the "sorry.jpg" image should be played.

In hindsight, we probably should have created a special "systemMediaType"
test attribute (which would take the native media type string), but we
thought that the mapping between URIs and Media Types was a rote exercise.
"systemMediaType" is on the wishlist for SMIL 3.0, presuming we get around
to doing that.

Rob
Received on Wednesday, 26 September 2001 03:18:32 UTC

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