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The HTML to Platform Accessibility APIs implementation guide requires AT to treat <img alt="" src=i> as 100% the same as <img role=presentation src=i > But such a change is likely to make many pages less accessible to AT users. Examples: Example 1: In this example, VoiceOver will contstruct a link text from the href URL. <a href="./"> <img src=i role=presentation title="Lorem Ipsum"> </a> Example 2: In this example, VoiceOVer will use @title as link text. <a href="./"> <img src=i title="Lorem Ipsum"> </a> Thus, as you can see, by making the empty img@alt="" a synonym for img@role=presentation, the treatment of existing web pages will be affected. Another problem of seeing them as 100% synonyms is: who wins if both are present and @alt e.g. is non-empty? If they are not 100% synonyms, then it is easier to see why role=presentation wins. Also, I believe there is a usecase for images with non-empty @alt text which nevertheless are presentational. (E.g. the @alt text could be purely decorational - to reflect that the image itself is purely some decorational symbols. )
Example from the wild: Mac OS X told to me to upgrade my printer today. This caused me to find that, on Apple support pages, the link to call the Apple Support Express Lane is an IMG link with a @title attribute in combination with an empty @alt: <a href="[link]"> <img src="http://images.apple.com/support/iknow/images/i_call_adv.png" alt="" title="Apple Support Express Lane"> </a> See the page: http://support.apple.com/kb/HT3669
Here is the approach which the 'HTML to Platform Accessibility APIs implementation guide' should take: 1. The AT should first run an algoritm to *calculate* whether the IMG is presentational or non-presentational 2. If it is non-presentational, AT should select the best text substitute When it comes to the algorithm to calculate whether IMG is presentational or not, then I have suggested how it should look in my 'Validity map for <img>': http://lists.w3.org/Archives/Public/public-html/2011Mar/0750 Two examples from that algorithm: * If IMG has non-empty @title, then AT should consider the IMG as non-presentational, regardless of @alt's value. * Ditto if IMG has @aria-labelledby - regardless of @alt's value.
Bug-triage sub-team adding the a11yTF keyword because this issue is already discussed in the TF and related to ongoing work regarding @alt validation.
With disagreement on how role=presentation should be handled in various cases, on HTML bug triage we agreed that it makes sense to treat these two examples in the same way.
With disagreement on how role=presentation should be handled in various cases, on HTML bug triage we agreed that it makes sense to treat alt="" and role=presentation in the same way.