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Re: ISSUE-2147 (external-refs confusing): Section on externally referenced documents confusing [Last Call: SVG 1.2 Tiny ]

From: Cyril Concolato <cyril.concolato@enst.fr>
Date: Tue, 14 Oct 2008 10:54:51 +0200
Message-ID: <48F45E5B.6050904@enst.fr>
To: SVG Working Group WG <public-svg-wg@w3.org>
Hi all,

SVG Working Group Issue Tracker a écrit :
> ISSUE-2147 (external-refs confusing): Section on externally referenced documents confusing [Last Call: SVG 1.2 Tiny ]
> http://www.w3.org/Graphics/SVG/WG/track/issues/2147
> Raised by: Doug Schepers
> On product: Last Call: SVG 1.2 Tiny 
> Cyril Concolato
> <http://lists.w3.org/Archives/Public/www-svg/2008Oct/0110.html>:
> [[
> * Section 14.1.6 Externally referenced documents 
> The section is quite hard to read and it's not easy to understand the difference between the processing of primary and resource documents. For example, instead of copy/pasting the "conceptual processing model" of primary documents for resource documents could you just give one unique paragraph? Could you highlight in the text the common points and differences? For example with the following structure
> definitions:
>  - primary document: referenced as a whole (no fragment). In SVG Tiny 1.2, it only concerns 'a', 'animation' and 'foreignObject' (as per restriction)
>  - resource documents: referenced using a fragment identifier. In SVG Tiny 1.2, it only concerns 'use' and 'foreignObject' (as per restriction)
> common points:
>  - processing is that events are fired, scripts are executed, ...
> differences:
>  - resource documents are loaded only once per primary document
>  - primary documents may be loaded multiple times
I attach a modified version of that section which I have rewritten according to the above plan. I tried not to remove any important text or nor added any new idea. However, I propose to remove the sentence in red.

> Could you also answer the following points:
>  - What about "externally referenced media" ? Does a primary document maintain a dictionnary of media resources? If a video is refered twice in the scene does this lead to two different ressources?
For this point, I suggest to add:
"Similarly to primary documents, multiple references to the same external media lead to separate media timeline."
It does not mention loading because in some cases (short clips), you might load and decode them only once.
The above sentence means that the following code will, at time 5, display 2 different frames of the same video: 

<video x="0" y="0" width="100" height="100" xml:id="v1" begin="0" xlink:href="http://www.example.org/myvideo.mp4"/>
<video x="0" y="100" width="100" height="100" xml:id="v2" begin="5" xlink:href="http://www.example.org/myvideo.mp4"/>

>  - What about externally referenced scripts ? 
Here I just want to clarify that if two scripts in the same scripting context point to the same script file, then the script is loaded only once. I propose the following sentence:

"Similarly to resource documents, in the case of multiple references, in the same scripting context, to the same external script file, the script file is processed once."

Cyril Concolato
Maître de Conférences/Associate Professor
Groupe Mutimedia/Multimedia Group
Département Traitement du Signal et Images
/Dept. Signal and Image Processing
Ecole Nationale Supérieure des Télécommunications
46 rue Barrault
75 013 Paris, France

Received on Tuesday, 14 October 2008 08:55:37 UTC

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