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Re: DIAGRAM project and image descriptions

From: Leif Halvard Silli <xn--mlform-iua@xn--mlform-iua.no>
Date: Fri, 18 Mar 2011 18:32:10 +0100
To: Charles McCathieNevile <chaals@opera.com>
Cc: Jonas Sicking <jonas@sicking.cc>, Laura Carlson <laura.lee.carlson@gmail.com>, Geoff Freed <geoff_freed@wgbh.org>, "public-html@w3.org" <public-html@w3.org>, HTML Accessibility Task Force <public-html-a11y@w3.org>
Message-ID: <20110318183210766938.b5da31e3@xn--mlform-iua.no>
Charles McCathieNevile, Fri, 18 Mar 2011 06:43:46 +0100:
> On Wed, 16 Mar 2011 00:51:12 +0100, Leif Halvard Silli:
>> Jonas Sicking, Tue, 15 Mar 2011 14:13:54 -0700:
>>> As far as I can see aria-describedby addresses this use case. I
>>> believe ARIA is no explicitly supported by HTML5 drafts.
>> Now I am surprised. Care to explain? See my concrete questions below.
>>>> On 2/25/11, Geoff Freed wrote:
>>>>> [ ... ] bear in mind that long descriptions are
>>>>> typically produced after the original content has been published.
>> Jonas, when produced after the original, how would you use
>> aria-describdby?
> Same as longdesc. By editing the page unless you put a placeholder there
> that temporarily isn't helpful. In other words, I don't think that is an
> issue for picking between the two.

Well, it seems to me that it is more complicated than that.

If @aria-describedby points to a  - visible or invisble - section on 
the same page via @aria-describedby, then that section will be 
presented to the user as a "string of text", where the sematnics of the 
markup will be ignored. So, if @aria-describedby poitns to to a 
<table>, for instance, then that table would be presented to the user 
more or less as a <table role="presentational"> table. And I don't 
think that *this effect* was the point with the table replacement for 
the diagram!

So, as this table example shows, it would frequently be better, even if 
the long description is on the same page, to use @longdesc.

However, it is up to Jonas to explain in what way he meant tha 
@aria-describedby could solve the task. Perhaps he had some usage in 
mind that that I don't know about.

>> [...]
>>>>> Furthermore, those hosted descriptions will be living documents which
>>>>> may need to be improved upon in a collaborative and moderated
>>>>> fashion. [...]
>> Jonas, how can aria-describedby address the use case of a description
>> that lives on another page?
> It can't. This is the major piece that longdesc can do which
> aria-describedBy doesn't.

Agree. But as I said: even if used on the same page, it is frequently  
better.  I think we can put it like this: @longdesc can point to a 
*alternative* description. Whereas @aria-describedby can give 
complementary information.

But again, may be Jonas have some info that I don't have.
leif halvard sili
Received on Friday, 18 March 2011 17:32:47 UTC

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