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Re: WAI-CG Consensus Recommendations on Alternative Text in HTML 5

From: Henri Sivonen <hsivonen@iki.fi>
Date: Wed, 15 Jul 2009 14:19:15 +0300
Cc: Janina Sajka <janina@rednote.net>, Sam Ruby <rubys@intertwingly.net>, Chris Wilson <Chris.Wilson@microsoft.com>, Michael Cooper <cooper@w3.org>, Dan Connolly <connolly@w3.org>, Mike Smith <mike@w3.org>, WAI XTech <wai-xtech@w3.org>, W3C WAI Protocols & Formats <w3c-wai-pf@w3.org>, "wai-liaison@w3.org Liaison" <wai-liaison@w3.org>, John Foliot <jfoliot@stanford.edu>, "public-html@w3.org WG" <public-html@w3.org>
Message-Id: <22E08E8E-D9B9-4C4C-A501-5D2BE209B7BF@iki.fi>
To: Jan Richards <jan.richards@utoronto.ca>
(Removed www-archive from CC, since it is redundant with other  
publicly-archived lists.)

On Jul 10, 2009, at 17:00, Jan Richards wrote:

> Henri Sivonen wrote:
>> (Added public-html to CC per HTML WG telecon minutes.)
>> On Jul 9, 2009, at 16:28, Jan Richards wrote:
>>> Henri Sivonen wrote:
>>> a. The tool leaves @alt out entirely, so that the code produced is  
>>> invalid.
>> That doesn't make sense. Invalid means that authors or tools acting  
>> on their behalf must not generate what is defined to be invalid.
>> It doesn't make sense to have a situation where ATAG 2.0 says "do  
>> X" and HTML 5 says "you must not do X". If there's consensus that  
>> it's good for ATAG 2.0 to say "do X", then we should make sure HTML  
>> 5 allows doing X--i.e. doesn't make it invalid.
>> (It's unclear to me where ATAG 2.0 actually says that alt can/ 
>> should be omitted in this case. Specifically, B.2.4.3 is too  
>> abstract for me to apply concretely to HTML5 with confidence that  
>> my application is what ATAG 2.0 meant.)
>
> JR: ATAG 2.0 does NOT say "include @alt" and it does NOT say "don't  
> include @alt". What it does say (in B.2.4.3) is that, if the human  
> author is no longer available (e.g., they closed Dreamweaver, their  
> phone auto-uploaded an image without their intervention), then the  
> authoring tool shouldn't automatically fill in any alternative  
> content (including @alt) using any text content that the user agent  
> could just as easily use BECAUSE doing so misleads the user agent  
> and end user into thinking that the @alt is more reliable than it is.

That much I understood. However, I'm interested in how the Authoring  
Tool Accessibility Guidelines Working Group expects HTML editors to  
comply with this requirement in practice (especially considering  
existing user agent behavior). As written, ATAG 2.0 doesn't provide  
concrete guidance for an HTML editor developer.

>>> b. The tool makes use of some kind of 'autogenerated' or 'missing'  
>>> attributes as per this paragraph in the consensus:
>>> "In order to address both the validity and human generation  
>>> concerns, we do not oppose the creation of 'autogenerated' and  
>>> 'missing' attributes where either one of these could be used to  
>>> make an image that does not have any human-generated text  
>>> alternatives valid. (Note: It is important that this marker is not  
>>> included in the alternative text string itself.)"
>> Is there a WAI CG consensus on what the marker should concretely be  
>> in the case I outlined? Do you mean an attribute named  
>> "autogenerated" or "missing"?
>
> JR: There was no concrete proposal on this because the task force  
> wanted to avoid being seen to dictate syntax to the HTML5 group  
> wherever possible.

But the task force wants to dictate syntax to the extent that the  
missingness be signaled with another attribute (of whatever name)  
rather than it being signaled by the absence of the alt attribute  
itself?

>> ATAG 2.0 B.2.4 doesn't help me understand what ATAG 2.0 wants HTML  
>> generators to do when there aren't "relevant sources" that B.2.4.3  
>> doesn't exclude and the user doesn't cooperate affirmatively per B. 
>> 2.4.2(a).
>
> JR: Remember: ATAG 2.0 applies to formats other than HTML5. For this  
> reason there is no validity requirement in ATAG 2.0 and therefore,  
> in the general case, alternative content attributes could just be  
> left out.  In the HTML5 case (where validity is required), you are  
> looking for a construct that means "this @alt is included for  
> validity but can't be trusted as alternative content" and that is  
> what you could get with attributes such as "autogenerated" or  
> "missing".

Or, alternatively, the validity definition for HTML5 could be such  
that it's valid for the alt attribute to be missing. That's simpler  
than having it present and having another attribute signal it's still  
actually missing.

Going back to http://www.w3.org/2009/06/Text-Alternatives-in-HTML5 , I  
have an additional question:
What's the utility of <img role=presentation src='...'> compared to  
<img alt='' src='...'>? Why does point #4 under "Specific  
recommendations regarding Short Text Alternatives" promote  
role=presentation over alt='' (no warning in the former case; warning  
in the latter case)?

-- 
Henri Sivonen
hsivonen@iki.fi
http://hsivonen.iki.fi/
Received on Wednesday, 15 July 2009 11:20:04 GMT

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