rationale for role=presentation use on images

Hi Laura,

role=presentaion can be placed on any element to indicate that it should not
be included in the accessible tree by the browser.
It is intended that user agents do not expose the element role via
accessibility APIs when role="presentation" is present on an element.

In HTML5 as per the current spec alt="" [1] on an image has an implied ARIA
role of presentation, although current implementations do not honour this.
use alt="" does not result in the img being removed from the accessible tree
by browsers. AT recognise alt="" as indicating that the image can be safely
hidden from the user, but their ways of handling this are not uniform.
 So in the spec role="presentation and alt="" are equivalent. Allowing
role="presentation" to be a conforming replacement for alt="" just
recognises what the spec states.

Why allow role="presentation" to act as an alternative to alt=""?
it is specified and implemented to do what alt="" is specified to do.
It is non specific, it works on all elements.
As per the rules specified in current spec pertaining to its use [1]  the
use of role="presentation" is not dis-allowed on the img element it is in
fact stated that it is the only role that can be applied to an img that has
an alt="", so you can do this:

<img role="presentation" alt="">

and nowwhere in the aria section [1] does it state you can't do this:

<img role="presentation">

but it will result in a conformance error, which appears both incongruous
and illogical.


[1]
http://dev.w3.org/html5/spec/content-models.html#annotations-for-assistive-technology-products-aria

-- 
with regards

Steve Faulkner
Technical Director - TPG Europe
Director - Web Accessibility Tools Consortium

www.paciellogroup.com | www.wat-c.org
Web Accessibility Toolbar -
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