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Image use cases that WCAG doesn't address

From: Henri Sivonen <hsivonen@iki.fi>
Date: Wed, 20 Aug 2008 12:10:48 +0300
Message-Id: <C758942C-8782-4D1C-A049-09881780661A@iki.fi>
To: public-comments-wcag20@w3.org

This comment is about Guideline 1.1 Text Alternatives, and this  
comment is about the substance of the guideline.

The HTML5 draft[1] gives advice and examples for including text  
alternatives for a variety of image uses cases. As far as I can tell,  
the following use cases aren't addressed by WCAG 2.0:

  * A diagram illustrates what is already said textually. (HTML5 says  
alt="" for this case.)

  * A user-uploaded image whose content is unknown to the programmer  
of the HTML generator that frames the image for Web display and the  
user hasn't supplied a text alternative. (HTML5 says to put the  
description of what kind of image the image is in curly braces in the  
alt attribute. E.g. a photo sharing site would use alt="{photo}".)

Proposed change:
I propose aligning with the HTML5 draft by saying that an image be  
marked as omissible from non-visual rendering if it illustrates what  
the surrounding prose already says.

I propose aligning with the HTML5 draft by saying that if the  
generator of markup does not have a text alternative available, it  
should use the natural-language expression describing the kind of  
content (to the precision known to the generator) as the text  
alternative and use a mechanism provided by the host format for  
marking the text as not really being a text alternative but an  
indication of what kind of non-text content is in question.

[1] http://www.w3.org/html/wg/html5/
Henri Sivonen
Received on Wednesday, 20 August 2008 09:11:31 UTC

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