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Re: ISSUE-2: What is the mime type of a media fragment? What is its relation with its parent resource?

From: Michael Hausenblas <michael.hausenblas@deri.org>
Date: Tue, 27 Jan 2009 13:30:56 +0000
To: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
CC: Media Fragment <public-media-fragment@w3.org>, RaphaŽl Troncy <Raphael.Troncy@cwi.nl>
Message-ID: <C5A4BD10.147C%michael.hausenblas@deri.org>


Silvia,

> The mime type is information that is provided by the server through
> http to the client. It relates to a resource. I wonder what happens if
> we specify a jpg thumbnail extract from a video through a fragment
> identifier ... since a fragment only identifies a subresource and not
> a new resource, we may not be able to do so. Yves, what do you think?

Though I'm not Yves, my take on it is:


Whenever we talk about URI semantics, we need to start with RFC3986 section
3.5: 
"The semantics of a fragment identifier are defined by the set of
representations that might result from a retrieval action on the primary
resource. The fragmentĻs format and resolution is therefore dependent on the
media type [RFC2046] of a potentially retrieved representation, even
though such a retrieval is only performed if the URI is dereferenced. If
no such representation exists, then the semantics of the fragment are
considered unknown and are effectively unconstrained. Fragment identifier
semantics are independent of the URI scheme and thus cannot be
redefined by scheme specifications."

>From RFC2046 we learn that the MIME Type Registrations for JPEG 2000
(ISO/IEC15444) is specified in RFC3745 [15] where no fragments are defined,
hence the general rules from RFC3986 apply.

My conclusion: in order to obey the rules of the game, we'd need to update
all registries of targeted media types.

Cheers,
      Michael

-- 
Dr. Michael Hausenblas
DERI - Digital Enterprise Research Institute
National University of Ireland, Lower Dangan,
Galway, Ireland, Europe
Tel. +353 91 495730
http://sw-app.org/about.html


> From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
> Date: Tue, 27 Jan 2009 23:40:54 +1100
> To: RaphaŽl Troncy <Raphael.Troncy@cwi.nl>
> Cc: Media Fragment <public-media-fragment@w3.org>
> Subject: Re: ISSUE-2: What is the mime type of a media fragment? What is its
> relation with its parent resource?
> Resent-From: <public-media-fragment@w3.org>
> Resent-Date: Tue, 27 Jan 2009 12:41:31 +0000
> 
> 
> On Tue, Jan 27, 2009 at 11:26 PM, RaphaŽl Troncy <Raphael.Troncy@cwi.nl>
> wrote:
>> 
>> ISSUE-2: What is the mime type of a media fragment? What is its relation
>> with its parent resource?
>> 
>> http://www.w3.org/2008/WebVideo/Fragments/tracker/issues/2
>> Raised by: RaphŽl Troncy
>> 
>> Related to a discussion started by Guillaume [1].
>> 
>> A media fragment URI can be used for addressing, for example, a particular
>> audio track of a mkv movie, or a particular key-frame of a video. What is
>> the resulting mime type of the secondary resource specified by the fragment
>> (audio, thumbnail, text)? Should we specify it in the recommendation?
>> What RFC3986 does say about the mime type of a fragment [2]?
> 
> The mime type is information that is provided by the server through
> http to the client. It relates to a resource. I wonder what happens if
> we specify a jpg thumbnail extract from a video through a fragment
> identifier ... since a fragment only identifies a subresource and not
> a new resource, we may not be able to do so. Yves, what do you think?
> 
> 
>> Side issue: in case we create a new resource (i.e. using the query '?'
>> parameter instead of the fragment '#' parameter), how do we make explicit
>> the relationship with the parent resource it was extracted from?
> 
> By leaving out the query part, we arrive at the parent resource.
> Specifying the parent resource should not be a problem for either
> query or fragment, I would say.
> 
> 
>> Do we use Link: rel="part_of" <video_uri> as suggested by Yves [3]?
> 
> I am not even sure we want to do these kind of URIs:
> http://www.annodex.net/cmmlwiki/OSSForum-Trailer.png?t=0:02:10
> 
> They should really be something more like:
> http://www.annodex.net/cmmlwiki/OSSForum-Trailer.anx?t=0:02:10&type=image/png
> 
> What do people think?
> 
> Cheers,
> Silvia.
Received on Tuesday, 27 January 2009 13:31:38 GMT

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