Re: Call for Review: HTML5 Image Description Extension (longdesc) Last Call

On Jul 17, 2013, at 9:30 AM, Charles McCathie Nevile <> wrote:

> Hi James,

Apologies for the delayed response. I've been on leave for a few weeks.

> On Tue, 16 Jul 2013 10:40:18 -0700, James Craig <> wrote:
>> I have an additional suggestion that I believe would help the acceptance of this document within the general working group. Add an informative section detailing several of the many cases where it is inappropriate to use @longdesc. For example…
> I think some of these are misplacing the cause of the problem they attempt to solve:
>> 1. @longdesc is inappropriate when an EPUB footnote is sufficient.
> Can you explain why it is "inappropriate" in terms of the problem that using it causes?
> In cases where apple users are targeted it is of course necessary to provide a fallback, since VoiceOver doesn't curently enable longdesc to be used, but that is not the same as causing harm by using the attribute.

AFAIK, longdesc doesn't work in any popular EPUB reader, unless you're counting desktop browsers. Footnotes, on the other hand, are well-defined and well-supported.

>> 2. @longdesc is inappropriate for Math. Use MathML instead.
>> 3. @longdesc is inappropriate for SVG graphics. Make the SVG DOM accessible instead.
>> 4. @longdesc is inappropriate for graphics of tabular data. Use an accessible table instead.
> In all of these cases, you appear to be blaming the use of longdesc as a repair strategy for an inappropriate design choice to which longdesc is orthogonal.

Not blaming. Just pointing out that these were listed as reasons that longdesc was "needed" when better mechanisms exist.

> Using images for mathematical content, or tabular data, is a known accessibility fail. But in a case where the image is there, using longdesc to mitigate the failure seems far better than simply throwing up your hands and saying "the world shooulda been different"...

Are you recommending images of math over MathML? If so, I don't agree with that at all. If you're argument is for the retrofit, I still think MathML is the better solution.

> In the case of SVG we currently have a disconnect between theory and reality. Although my text on SVG accessibility is (after more than a decade) pretty solid on how to make the DOM accessible, in practice I believe that is only useful for the relatively small proportion of users who have VoiceOver. I realise it is bigger in some markets, but the best figures I can get for Russia suggest that is under 5%. In this situation, while I strongly support the idea that the DOM should be accessible, it seems that a longdesc as a temporary repair strategy for windows users - i.e. the vast bulk of real people - is actually a very helpful thing to do.
>> These should probably be added to the WCAG 2.0 Techniques documents as well.
> We certainly need to look at the WCAG 2 techniques document, and upgrading it.
> cheers
> Chaals


Received on Tuesday, 13 August 2013 23:46:58 UTC