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Re: ISSUE-30 (Longdesc) Change Proposal

From: Jonas Sicking <jonas@sicking.cc>
Date: Tue, 27 Oct 2009 12:15:26 -0700
Message-ID: <63df84f0910271215o644bac72kf6dd6b556311a716@mail.gmail.com>
To: Leif Halvard Silli <xn--mlform-iua@xn--mlform-iua.no>
Cc: Charles McCathieNevile <chaals@opera.com>, "public-html@w3.org" <public-html@w3.org>
On Tue, Oct 27, 2009 at 7:09 AM, Leif Halvard Silli
<xn--mlform-iua@xn--mlform-iua.no> wrote:
>>> However, as the rest of my letter hinted, @longdesc and aria-describedby
>>> are
>>> different. @longdesc has a much more fixed behavior than aria-describedby
>>> has - and is much more single purposed than aria-describedby. See the
>>> other
>>> replies in this thread. The primary specialty of longdesc is simply that
>>> it
>>> is only meant for IMG, FRAME and IFRAME - the rest of its inherited
>>> behavior
>>> follows from that.
>> I agree that @longdesc and @aria-describedby aren't exactly the same.
>> However they are very similar.
> Everything with a link is "similar". But normally, if one element can take
> IDREFS only and another can take a single, complete URI, only, then we don't
> consider them similar.

If two features are designed to solve the same problem, then I think
they are similar enough that having both is a loss for all involved

I would strongly argue that having more accessibility attributes does
not mean that we'll have a more accessible web. In fact, I would say
it's more likely to have the opposite result. It's much more valuable
to have a simple clear message for how to make a page accessible by

"To include a description use the @described-by attribute, see here
for a couple of examples"

Than to say

"To include a description use the @described-by attribute or the
@longdesc attribute, and on tables you can use the @summary attribute.
@described-by is what you should use in situation X, @longdesc is for
situation Y. In situation Z you can use either. If you use both then A
will happen. Here are some examples"

I'm worried if our message is the latter people are more likely to not
add anything and instead leave it for later when they have time to
figure out what the right thing to do is. Especially since "have time"
is something that's rare.

>> Also, syntactically @aria-describedby has a larger syntax if the
>> description is in an external document.
> In addition to require a much more verbose *markup*, there are also
> "expected effect" differences. See John's message [1] (and my reply).
> [1] http://www.w3.org/mid/009901ca566c$a296a9c0$e7c3fd40$@edu

I don't agree there's an expected difference.

Comparing the markups:

<img aria-describedby="desc">
<a href="description.html" id="desc">...</a>


<img longdesc="description.html">

In both cases I would expect AT to indicate to the user that a
description is available for the image. And if the user chooses to
access that description, there is no reason the UA couldn't perform
exactly the same action in both examples. Be that navigating to
"description.html" using the current tab, opening a new tab, reusing a
dedicated "description" tab. Or not navigating at all and simply
reading the contents of description.html to the user.

In neither case there is a specification that mandates how that
description is presented to the user.

There *is* specified behavior for if the user activates the <a> link
in the first example. However that behavior doesn't need to be
followed if the user accesses the description for the image.

/ Jonas
Received on Tuesday, 27 October 2009 20:21:33 UTC

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