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Re: Conditional Content.

From: Ian B. Jacobs <ij@w3.org>
Date: Fri, 23 Aug 2002 10:22:27 -0400
Message-ID: <3D664523.60507@w3.org>
To: Jim Ley <jim@jibbering.com>
CC: w3c-wai-ua@w3.org

Jim Ley wrote:
> "Ian B. Jacobs" <ij@w3.org>
> 
>>If the content of the foreignObject is defined by specification S,
>>and S says that it's conditional content, and the user agent
>>implements S, then the user agent is responsible for making
>>it available. The "user agent" may include a plug-in specifically
>>for this rendering.
> 
> 
> My concern was that SVG defines the content of switch as conditional
> content, and therefore when the foreignObject is in a switch element it
> is conditional content and therefore a UA would have to render it (even
> though it doesn't know anything about HTML, or MathML or whatever)
> 
> ie 23.4 in http://www.w3.org/TR/SVG11/extend.html
> 
> which defines conditional content of a foreignObject containing some
> HTML, and some SVG text, the UA can safely ignore the HTML portion if it
> doesn't understand HTML?

In 23.4, the SVG spec says:

  "It is not required that SVG user agent support the ability to 
invoke other arbitrary user agents to handle embedded foreign object 
types;"

UAAG 1.0 doesn't require it either. UAAG 1.0 doesn't require
that a user agent support any particular content format.

You (or UAAG 1.0) can't hold the user agent responsible for
formats it doesn't recognize. If the user agent implements
HTML, then you can choose whether to make a claim about
support for it.

UAAG 1.0 section 3.1.2 [1] states that a conformance profile
must include the following:

  "Information about one or more specifications (e.g., markup
   languages, style sheet languages, APIs, etc.) implemented to
   satisfy the requirements of this document. A user agent must
   satisfy the requirements identified by the profile for at least
   these specifications. A user agent is not required to satisfy the
   identified requirements for other implemented specifications
   except when a content type label definition states otherwise."

Thus, it is possible to claim conformance for an SVG agent and
to not claim conformance for embedded content in other formats.

  _ Ian

[1] 
http://www.w3.org/TR/2002/WD-UAAG10-20020821/conformance#profile-structure

-- 
Ian Jacobs (ij@w3.org)   http://www.w3.org/People/Jacobs
Tel:                     +1 718 260-9447
Received on Friday, 23 August 2002 10:26:21 GMT

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