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Re: New issue: IMG section of HTML5 draft contradicts WCAG 1 & WCAG 2 (draft)

From: scott lewis <sfl@scotfl.ca>
Date: Fri, 11 Apr 2008 07:35:36 -0600
Cc: Steven Faulkner <faulkner.steve@gmail.com>
Message-Id: <45809715-7C5B-459C-8F11-606C4BFBF2D9@scotfl.ca>
To: HTML Working Group <public-html@w3.org>

On 2008-04-11, at 0605, Steven Faulkner wrote:
>
> Two images without explicitly associated text alternatives.
> 1 is an image is decorative that the author has accidently left off
> the alt, the other is "critical content" that the author could not
> provide an alt for whatever reason
> 1 can be safely ignored, the other should be brought to the attention
> of the user.
>
> <img src="abc.jpg">
>
> <img src="xyz.jpg">
>
> How is Assistive Technology  supposed to reliably determine this?
> Given that these two images could be the same, but their meaning
> differ widely depending on the intent of the author in regards to
> their use.
>
> regards
> steve


Assuming that the abc image is the meaningful one:

<img src="abc.jpg">
<img src="xyz.jpg" alt="">

The absence of an @alt indicates that the image may be meaningful.   
The presence of an empty @alt indicates that the image is decorative.   
This assumes, of course, that the author is interested in making the  
images accessible.  If the author is completely disinterested in  
accessibility, then the author can simply omit the @alt and AT will  
"fail safe" by informing the user that there are potentially  
meaningful images on the page.


Demanding the @alt is simply going to lead to:

<img src="abc.jpg" alt="">
<img src="xyz.jpg" alt="">

In which the author has done the least amount of work to satisfy the  
validator.  It impossible for AT to determine which image is meaningful.


Requiring a magic flag value for absent alt text will create the  
possibility of:

<img src="abc.jpg" alt="MAGIC FLAG VALUE">
<img src="xyz.jpg" alt="MAGIC FLG VALUE">

or:

<img src="abc.jpg" alt="x">
<img src="xyz.jpg" alt="x">

Here the decorative xyz image is erroneously flag as meaningful  
because the author (disinterested in accessibility) has again done the  
least amount of work necessary to satisfy the validator.  In the first  
case the author has attached the magic flag value to each image, but  
accidentally mistyped it on one.  In the second case the author has  
provided a useless (yet valid) value for the @alt.


scott.
Received on Friday, 11 April 2008 13:36:19 UTC

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