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Re: HTML Action Item 54 - ...draft text for HTML 5 spec to require producers/authors to include @alt on img elements.

From: Christophe Strobbe <christophe.strobbe@esat.kuleuven.be>
Date: Thu, 22 May 2008 12:57:00 +0200
Message-Id: <6.2.5.6.2.20080522124411.0355f840@esat.kuleuven.be>
To: wai-xtech@w3.org


At 00:26 22/05/2008, James Graham wrote:

>Steven Faulkner wrote:
>>hi Jgraham
>>>That would appear to preclude requirements such as:
>>>"The alt attribute [...] must contain a text alternative that 
>>>serves the equivalent purpose as the image. What is to be 
>>>considered an equivalent purpose, depends on the way an image is used."[1]
>>well, no, there are methods for deciding the appropriateness of  text
>>alternatives according to the context the image is used in. These are
>>described in WCAG 2.0 for example.
>
>Do you mean [1] or something else? All the information in that 
>document assumes that the assessor knows the purpose of the image;

Yes.

>that is to say the author's intent.

Not quite. An image always has a certain purpose for sighted users 
and that purpose is normally clear (unless the user interface design 
was badly thought through so communication with sighted users fails). 
The text alternative must convey that purpose to users who cannot 
perceive the image. If a sighted user does not need to ask the author 
what he or she intended to convey by means of the image, why would it 
be necessary to consult the author in order to evaluate the 
appropriateness of the text alternative?
I admit that there are edge cases (often about whether an images is 
decorative or not), but WCAG 2.0 was written to be independent of 
author intent.


>Sure, in many cases it would be possible to guess the author's 
>intent from the page* but that is also true for many of the other 
>conformance requirements that require knowing the author's intent. 
>Indeed, it is often possible to guess whether it was practical for 
>the author to provide alt text or not depending on the nature of the 
>image, how it was uploaded, how many other images were uploaded, and 
>so on. Nevertheless only the author can be considered an 
>authoritative source for any of this information.
>
>* Although it is possible to construct cases where it is not; 
>consider a psychological test in which the user is asked to perform 
>some task involving images but the experimenter is looking for some 
>subconcious response not directly related to the task

That would fit under "If non-text content is a test or exercise that 
must be presented in non-text format, then text alternatives at least 
provide descriptive identification of the non-text content" in the 
document that you referenced.

>[1] 
>http://www.w3.org/TR/2008/WD-UNDERSTANDING-WCAG20-20080430/text-equiv-all.html

Best regards,

Christophe


>--
>"Mixed up signals
>Bullet train
>People snuffed out in the brutal rain"
>--Conner Oberst

-- 
Christophe Strobbe
K.U.Leuven - Dept. of Electrical Engineering - SCD
Research Group on Document Architectures
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Received on Thursday, 22 May 2008 10:57:50 GMT

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