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Re: Assumption in the SVG specifications

From: Dave Singer <singer@apple.com>
Date: Thu, 31 Aug 2006 14:19:20 +0200
Message-Id: <p0623099dc11c825da83c@[]>
To: Chris Lilley <chris@w3.org>
Cc: www-svg@w3.org

At 13:22  +0200 31/08/06, Chris Lilley wrote:
>On Thursday, August 31, 2006, 12:58:32 PM, Dave wrote:
>DS> It seems that the SVG specifications assume that SVG is the only
>DS> vector format in existence.  Quoting one of the specs on the site:
>DS> "In SVG Tiny 1.2, the 'image' must reference content that is a raster
>DS> image format, such as PNG and JPG. SVG Tiny 1.2 does not allow an SVG
>DS> document to be referenced by the 'image' element; instead, authors
>DS> should use the 'animation' element for referencing SVG Documents."
>DS> and
>DS> "The 'animation' elements specifies an SVG document providing
>DS> synchronized animated vector graphics. "
>Thats an error. Indeed it was already discussed, and we agreed that 
>the animation element is for general animated vector graphics 
>(although a conformant viewer is only required to render the 
>contents if they point to SVG).
>It seems that wording did not get updated; we will fix this error.
>DS> Could someone clarify if the intent of this specification was to
>DS> exclude the use of all other possible static vector formats?
>No, that was not the intent. The conformance requirement and the 
>intent of the element were conflated in the text you cite; these 
>will be clearly separated.

Chris, thanks

this helps, but I want to be clear.  The "animation" element is 
supposed to be used for any vector-based content, even if the format 
doesn't permit any animation as such, or the image in question is 
not, in fact, animated?

I think there is a deeper problem here.  The tags 'image', 'video', 
and 'audio' ask these questions about the content
a) does it have a visual presentation?
b) does it have an audible presentation?
c) does the presentation change over time?

whereas the 'animation' tag seems to ask a completely orthogonal question
i) is it coded using vectors or rasters?

The first three questions enable the client to know 'does it use 
screen real-estate?', 'do I need to connect to an audio output 
device?' and 'do I need to manage the content handler providing a 
visual presentation that changes over time, might the user want 
(perhaps) at least a play/pause control?'.  They are all questions 
about how the content is *presented*.  The animation tag seems to be 
asking about how it is *coded*, by contrast, and not surprisingly, 
this raises questions.

I have to say I am quite surprised that the answer to the question 
"what tag should I use to display an illustrator image" is not 
"image" but "animation", but that the answer would change if I 
rendered the image *to the same visual quality and effect* to a PNG 
file and then embedded that (the user should be able to detect no 
difference at all).
David Singer
Apple Computer/QuickTime
Received on Thursday, 31 August 2006 12:24:42 UTC

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