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Re: ISSUE-2350 (unknown element fallback): Specify that unknown elements are treated as <g> elements for the purpose of rendering [SVG 2.0]

From: Erik Dahlstrom <ed@opera.com>
Date: Fri, 09 Jul 2010 11:00:14 +0200
To: "SVG Working Group WG" <public-svg-wg@w3.org>
Message-ID: <op.vfkjalxkgeuyw5@localhost>
On Fri, 09 Jul 2010 00:15:34 +0200, SVG Working Group Issue Tracker  
<sysbot+tracker@w3.org> wrote:

>
> ISSUE-2350 (unknown element fallback): Specify that unknown elements are  
> treated as <g> elements for the purpose of rendering [SVG 2.0]
>
> http://www.w3.org/Graphics/SVG/WG/track/issues/2350
>
> Raised by: Doug Schepers
> On product: SVG 2.0
>
> SVG 1.1 says, in  
> http://www.w3.org/TR/2003/REC-SVG11-20030114/extend.html :
> [[
> 23.1 Foreign namespaces and private data
>
> SVG allows inclusion of elements from foreign namespaces anywhere with  
> the SVG content. In general, the SVG user agent will include the unknown  
> elements in the DOM but will otherwise ignore unknown elements. (The  
> notable exception is described under Embedding Foreign Object Types.)
> ]]
>
> I think we should be more precise about this, and say that unknown  
> elements are treated as <g> elements for the purpose of structure,  
> rendering, and inheritance, and that their child elements still render.   
> This is an SVG extensibility point for new SVG elements (as well as  
> other namespaced content), and would allow authors to define fallback  
> content for the new element, per spec.
>
> For example, if we add a connector element, authors could also specify a  
> simple path as a child, so that older UAs would still have something to  
> render, even if it isn't as functional as the connector element.

You are aware that this goes against what is specified in SVG Tiny 1.2  
[1]? Your fallback content wouldn't be rendered by SVG Tiny 1.2 compliant  
engines.

In short, I disagree with the proposal to render child elements of unknown  
elements. However I wouldn't mind if we adopted the wording in [1] to SVG  
1.1F2 to further clarify handling of unknown attributes/elements.

Cheers
/Erik

[1] http://www.w3.org/TR/SVGTiny12/implnote.html#UnsupportedProps

-- 
Erik Dahlstrom, Core Technology Developer, Opera Software
Co-Chair, W3C SVG Working Group
Personal blog: http://my.opera.com/macdev_ed
Received on Friday, 9 July 2010 09:00:49 UTC

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