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Re: ISSUE-30 (Longdesc) Change Proposal

From: Leif Halvard Silli <xn--mlform-iua@xn--mlform-iua.no>
Date: Fri, 30 Oct 2009 13:30:28 +0100
Message-ID: <4AEADC64.9090804@xn--mlform-iua.no>
To: Joshue O Connor <joshue.oconnor@cfit.ie>
CC: Jonas Sicking <jonas@sicking.cc>, John Foliot <jfoliot@stanford.edu>, Charles McCathieNevile <chaals@opera.com>, public-html@w3.org
Joshue O Connor On 09-10-30 12.24:

> Jonas Sicking wrote:

   [...]

>>>> * Simpler AT tools
>>> ??  AT *today* supports @longdesc - I personally do not think that they
>>> are going to now remove this support in future versions. Why would they?
>>> Just to replace it with aria-describedby? Really?
> 
> I doubt it. The two will probably be supported in tandem - for legacy
> reasons - even if the use of @longdesc is very small. Its a case of
> those who find it useful - well, find it useful.


One cannot simply replace @longdesc with @aria-describedby 
because, since aria-describedby="link" is not a link. Supporting 
aria-describedby and aria-labelledby therefore requires more than 
just switching the attributes.

   [...]

> Charles McCathieNevile wrote:
> 
>> It is possible that we should deprecate longdesc - point out that it is
> obsolete, *if* aria-describedby can do the same job in the real world.
>> But I don't think that day has yet arrived, and until it does, leaving an existing and well-described HTML feature that is useful 
>> (admittedly not to the whole universe, but to some people in some cases) in the spec seems a more rational choice. 
> 
> IIRC - The only thing that @longdesc trumps @aria-described by with is
> the ability to reference a URI, and @aria-describedby is limited to an
> IDREF. This could well change - but probably not until HTML 5 reached TR
> - so it could be HTML 6 that has this one. I doubt there will be changes
> like this in ARIA at this late stage. If it could happen though, that
> would be a welcome change.

I agree: That @longdesc is a link is the key. @longdesc has other 
advantages as well, but they are all linked (sic!) to the fact 
that it is a link.

I wonder if it will be possible to make aria-describedby into a 
link, though. There seems to me to be a whole host of problems 
linked to that.

Consider:
  aria-describedby="link"
          longdesc="link"

The former points to somewhere on the same page. The latter points 
to another page with the resource name "link".

To make it possible to discern IDREFs from links you would then 
have to use full URIs, I suppose. Cumbersome. Prone to errors. 
Seems better to eventually introduce a aria-longdesc="" or 
aria-link="", then.

Though I am not at all certain that the hypothetical @aria-link 
would work like @longdesc. Would it?

The purpose of ARIA seems to me to be to let the UA "compute" the 
A11Y layer on behalf of the author and the user. Whereas @longdesc 
as well as "normal fallback" (such as @alt content and the 
fallback of <object>) are "real" fallback that relies on regular 
hyper text.
-- 
leif halvard silli
Received on Friday, 30 October 2009 12:31:03 GMT

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