Re: Add rationale or exclude role="presentation", aria-labelledby & aria-labelled attributes from alt change proposal? Help needed. (was Re: ISSUE-31 Change Proposal)

Hi Laura,

> On 6/23/10, Maciej Stachowiak<mjs@apple.com>  wrote:
>> * aria-labelledby attribute present (non-empty only)
>>* aria-label attribute is present (non-empty only)

as Steve has already provided a rationale for role="presentation" I see
that "aria-labelledby" and "aria-label" (not "aria-labelled") haven't
been explained yet.

aria-labelledby refers to the ID of another element containing a label
for the image. It adds a relationship between the image and the element
acting as a label. Thus there is text that can be read by AT, and the
alt attribute on the image should be omitted to avoid redundancy, i.e.
reading the text twice.

aria-label is an attribute of the image element and has the same
function as the alt attribute. Therefore it is sufficient if either is
present.

aria-label has been added rather late to the ARIA spec and thus isn't on
the radar of many people. Rich Schwerdtfeger once explained that is has
been requested by a browser vendor if I remember it right, he can tell
you the raison d'être.

Cheers,
   Martin