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Re: Identifying vs Describing media URI fragments

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Wed, 24 Sep 2008 21:55:18 +1000
Message-ID: <2c0e02830809240455p6effaa3dw6170d5ffafa50c39@mail.gmail.com>
To: "Yves Lafon" <ylafon@w3.org>
Cc: "RaphaŽl Troncy" <Raphael.Troncy@cwi.nl>, "Media Fragment" <public-media-fragment@w3.org>

On Wed, Sep 24, 2008 at 9:44 PM, Yves Lafon <ylafon@w3.org> wrote:
> On Wed, 24 Sep 2008, Silvia Pfeiffer wrote:
>
>>> I think Raphael's point is: should the fragment be self-descriptive
>>> enough a
>>>  "kiss-scene" are equivalent. In both case, the machine
>>>  will not understand what this fragment is about ]] ).
>>
>>
>> If we only identify that it is a fragment of a *video*, but not what
>> its semantics are, that comes through the media type of the resource,
>> right?
>
> You have to know it beforehand, if you want to use HTTP range request using
> units other than bytes. It really depends on how you plan to interact with
> the server.
>
>>> This is especially critical when you want the machine to retrieve only
>>> the
>>> fragment and not the whole resource; as opposed to giving a first class
>>> identification to fragments (ie: giving them the resource status).
>>
>> Do you mean that we need to have semantics to identify what segment of
>> a video we need to retrieve?
>
> Well, only if you access those fragments using difference resource
> identifiers, fragments are just part of the same resource.

Ah! This is where the discussion becomes interesting! We are now
talking about URI fragments and not media fragments. So we need to get
our terminology and understanding right.

I have had a long discussion about using "#" in URIs to identify media
fragments with the URI WG. Everything that is specified in a URI
fragment is only local to the client and cannot be transferred to the
server. In fact, after my discussion, they fixed a bug in Apache where
the fragment was sent and accepted by Apache. Apache now does not
accept URI fragments any more. Therefore, if we want to use a URI
mechanism to gain access to media fragments (i.e. subparts of media
files), we have to use a different mechanism. That's why the
temporalURI spec uses queries ("?") instead of fragments.

I am assuming we are trying to work within the boundaries of other
given standards to do our specifications. It is the least complicated
way. :-)

Cheers,
Silvia.
Received on Wednesday, 24 September 2008 11:55:55 GMT

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