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Re: [1.2T-LC] 16.2.9 values attribute 'extended syntax' (ACTION-2318, ISSUE-2084)

From: Doug Schepers <schepers@w3.org>
Date: Fri, 17 Oct 2008 14:34:10 -0400
Message-ID: <48F8DAA2.3070001@w3.org>
To: "Dr. Olaf Hoffmann" <Dr.O.Hoffmann@gmx.de>
CC: www-svg@w3.org

Hi, Dr. Olaf-

Dr. Olaf Hoffmann wrote (on 10/1/08 10:00 AM):
> 
> it is surprising, that there is already a lot of SVGT1.2 content with invalid
> values for the 'values' attribute, because such 'extended syntax' is nonsense
> both for SMIL and for SVG1.1 too.
> For me this indicates more simple errors from authors or editors, especially
> because the adobe plugin, for several years the most used viewer for animated
> SVG content has a quite different '(error) management' for such wrong syntax
> (if it is wrong and does not specify an allowed empty value, it indicates an
> error and assumes one more value than the number of semicola. If an empty
> value is possible, an empty value is correctly interpreted as empty value).
> Every author testing content with the adobe plugin should have noted
> the error and should have already fixed it before publication.
>
> Typically if I find errors in my documents or scripts, I simply fix them and
> do not expect, that the specification is modified to fix my own errors. 
> And even more, no one can expect, that the behaviour of already published
> versions of viewers can be modified, therefore this 'extended syntax' should
> never be used to ensure better backwards compatibility with older viewers,
> therefore such a superfluous trailing semicolon needs to be fixed anyway to
> ensure a predictable behaviour.
> Especially there is no benefit for authors or users from this 'extended
> syntax'. 
> The opposite is the case with something like "/a.txt; ; /b.txt; ;" to get the
> desired effect of an  empty list item only for SVGT1.2.
> For implementors of SVG1.1, SVGT1.2 and SMIL it gets even worse, because 
> they have to implement it differently for SVGT1.2 without any advantage for
> anyone.
> 
> My suggestion is to skip this SMIL and backwards incompatibility completely
> and to help authors to fix their documents, if it is known, which authors
> produce so much erratic content without testing it.
> If such content is already mentioned in the specification, some editor should
> know at least some of these authors and how much invalid content it is. Maybe
> references would be useful too for others interested in helping those authors.
> This is more friendly for those authors as to brand or to stigmatise them to
> be guilty to corrupt the well thought out SMIL syntax.


Actually, the situation is that one of the more popular SVG animation
authoring tools, Ikivo Animator, makes this mistake in its output.  This
resulted in a large amount of faulty content.  Because this was a fairly
obscure point, SVG 1.2 Tiny viewers adapted to the content.  However, we
have spoken to Ikivo about this problem, and they have agreed to change
this error in future releases of their product.

In the meantime, we have to accommodate the current behavior of viewers,
and to inform authors about the potential pitfall of the trailing
semicolon syntax.  I have therefore changed the passage in question to
permit, but not mandate, this behavior, but also to caution authors and
authoring tools against using this syntax.

 http://dev.w3.org/SVG/profiles/1.2T/publish/animate.html#ValuesAttribute

We will examine this more deliberately in SVG 2.0 Core.

Please let us know if this satisfies your comment.

Regards-
-Doug
Received on Friday, 17 October 2008 18:34:19 GMT

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