Re: Need differentiator between "no alt text provided" and "no alt text necessary"

I meant to add a potential solution as to the wording. The current  
wording is:

If the src attribute is set and the alt attribute is not
The image might be a key part of the content, and there is no textual  
equivalent of the image available.

Source: http://dev.w3.org/html5/spec/Overview.html#the-img-element

I believe this wording would be more clear.

If the src attribute is set and the alt attribute is not
The image is assumed to be a key part of the content, and there is no  
textual equivalent of the image available.



On Feb 2, 2009, at 2:57 PM, James Craig wrote:

> Please keep me in the CC replies b/c I'm not on public-html. This is  
> the tail end of a thread from the PFWG.
>
> Begin forwarded message:
>
>> James Craig wrote:
>>
>>> Simon Pieters wrote:
>>>
>>>> So do you think HTML5 should go back to support the case where an  
>>>> image needs a label (or textual equivalent) but lacks one?
>>>
>>> I think so, yes.
>
> …snip…
>
>>>> How do you envision ATs to differentiate [these cases]?
>>>
>>> The language is for any software (including search engines), not  
>>> just UA/AT. If a search engine (or a future implementation of AT)  
>>> has the capability, it may try to use optical character  
>>> recognition on images that are determined to be meaningful but  
>>> without alternative text.
>
> Or to change the navigation mechanism based on that difference.
>
> For example, at least one screen reader has a preference to allow  
> you to navigate no images, all images, or only images with a  
> description. An image with a role of presentation should not be  
> treated as an image at all, so it should no be navigated to, even if  
> the user setting is to navigate all images. However, if the user's  
> preference is to navigate only to images with descriptions, then  
> there would be no navigational difference between a presentational  
> image and a meaningful image that just lacks appropriate alternative  
> text.
>
>>>> Why is <img alt="" noalt> better than just <img>?
>>>
>>> As long as there is a clear differentiation between these three  
>>> states, I'm okay with whatever the markup looks like.
>>>
>>> 1. Presentational image (no alternative text necessary)
>>> 2. Meaningful image (no alternative text provided)
>>> 3. Meaningful image (alternative text provided)
>>
>> Now we're getting somewhere. :-) You should express the above  
>> points on public-html or somewhere public that gets on the editors'  
>> radar.
>
> So, to the public-html group:
>
> The reason there needs to be a differentiator is because each host  
> language (in this case, HTML 5) needs a way to determine when an  
> image should use the "presentation" role [1] and when it should use  
> the default "img" role so the user agent can convey the role to an  
> assistive technology API. An author or an authoring tool may have  
> that information, but there is currently no way to convey it in the  
> language.
>
> 1. http://www.w3.org/WAI/PF/aria/#presentation
>