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Re: values of requiredExtensions to use XHTML/MathML (ACTION-2193 ISSUE-2053)

From: Doug Schepers <schepers@w3.org>
Date: Wed, 17 Sep 2008 16:36:56 -0400
Message-ID: <48D16A68.2000407@w3.org>
To: www-svg@w3.org
CC: fred.wang@free.fr

Hi, Fred-

Coming so close to our Last Call period as your comment was, we went
ahead and treated it as an LC comment.

I'm pleased to say that the SVG WG agreed with your comment, and we have
clarified the wording of the 'requiredExtensions' attribute [1] to say
generically that the namespace of the language should dictate the value
of 'requiredExtensions'.  We also added examples to the <foreignObject>
definition [2] that we hope will help inform authors on how to do this,
and propagate that way as well.

Please let us know promptly whether the new wording satisfies your comment.

I also have a follow-up question, inline...

fred.wang@free.fr wrote (on 8/12/08 3:23 AM):
> 
> In the "Guidelines for Graphics in MathML 2", Michael Kohlhase gives an example
> where he uses a foreignObject to include mathematical formulae inside SVG
> graphics, in combination with a <switch/> to provide an alternate text. The
> requiredExtensions has the value "http://www.w3.org/1998/Math/MathML":
> 
> http://www.w3.org/Math/Documents/Notes/graphics.xml#mathml-in-svg-guidelines
> 
> Similarly, when Amaya creates XHTML content in SVG, a
> requiredExtensions="http://www.w3.org/1999/xhtml" is attached to a
> <foreignObject/>. The problem is that these two possible values are not clearly
> indicated in the specifications:
> 
> http://www.w3.org/TR/SVG11/extend.html#AnExample
> http://www.w3.org/TR/XHTMLplusMathMLplusSVG/#howto-xhtml
> 
> As a consequence, this use of <switch> to allow alternate content is quite
> ironically a problem for interoperability because browsers behave differently:
> 1) Amaya can display MathML and XHTML inside SVG. It accepts
> "http://www.w3.org/1998/Math/MathML" and "http://www.w3.org/1999/xhtml" values.
> 2) Firefox can display MathML and XHTML inside SVG, but since it refuses
> "http://www.w3.org/1998/Math/MathML" and "http://www.w3.org/1999/xhtml" values,
> it displays the alternate content.

Can you point to examples of this working in Firefox?  I'm curious to
see it.


> 3) Other browsers that can't render MathML/XHTML in SVG should display the
> alternate content.
> 
> Can the SVG WG indicates in the spec that browsers able to display MathML and
> XHTML inside SVG should recognize the two values
> "http://www.w3.org/1998/Math/MathML" and "http://www.w3.org/1999/xhtml"?


[1]
http://dev.w3.org/SVG/profiles/1.2T/publish/struct.html#RequiredExtensionsAttribute
[2]
http://dev.w3.org/SVG/profiles/1.2T/publish/extend.html#ForeignObjectExamples

Regards-
-Doug, on behalf of the SVG WG
Received on Wednesday, 17 September 2008 20:37:32 GMT

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