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RE: longdesc requirements Re: alt tags for graphs

From: Jonathan Avila <jon.avila@ssbbartgroup.com>
Date: Mon, 1 Apr 2013 10:00:05 -0400
Message-ID: <ff03d43b19ce3e6ae5802ebb6d0a8e5e@mail.gmail.com>
To: Charles McCathie Nevile <chaals@yandex-team.ru>, "Frank M. Palinkas" <fmpalinkas@gmail.com>, David Woolley <forums@david-woolley.me.uk>
Cc: "Mattingly, F Darrell" <darrell.mattingly@uky.edu>, WAI Interest Group <w3c-wai-ig@w3.org>, "Guettler, Karen M" <kmguet2@uky.edu>
[Chaals wrote] (do you have a pointer to that mail? I can't find it :( )

Here is the link to the post that I approved but it evidently was never
posted to the public HTML a11y list.
http://www.w3.org/Mail/review?id=ca4a184393bfadaa22d7  This is not the first
time this has happened.

[Chaals wrote] I'm not sure I understand. The requirements on user agents
are:

> User agents should make the link available to all users through the
> regular user interface.
> User agents should expose the link to relevant APIs, especially
> accessibility-oriented APIs.
> User agents should enable users to discover when images in a page contain
> a long description.

> Are you simply proposing that the "should" requirements be strengthened to
> MUST? And that there should be a matching requirement to make them
> keyboard accessible?

Yes, that is what I was hoping.

> I would certainly be happy if the should listed become musts. If you would
> like to raise a bug, please do, or I can do it if you prefer.

> I don't think that the normative requirement to be keyboard-accessible
> belongs in this spec - it is a general  accessibility requirement for User
> Agents that run on devices where keyboards can be used, so is in UAAG. I
> would propose instead adding an informative note and a reference, if you
> think it is necessary to make this particular point.

I would be happy with that.

[Chaals wrote]
> It would surprise me, as the person who wrote the text of the longdesc
> spec. I would think the HTML spec is wrong to insist on that, and would
> not want to follow. But I just read
> http://www.w3.org/TR/html5/embedded-content-0.html#the-img-element (the
> Candidate Recommendation draft) all the way through, and as far as I can
> tell it doesn't have that requirement.

Past discussions about the topic of displaying alt text for images tend to
go back to the requirements I pulled from the HTML 5.1 nightly draft below
(which historically has been the same in earlier specifications).

http://www.w3.org/html/wg/drafts/html/master/embedded-content-0.html#alt

"If the image is available and the user agent is configured to display that
image, then the element represents the element's image data."

"Otherwise, the element represents the text given by the alt attribute. User
agents may provide the user with a notification that an image is present but
has been omitted from the rendering."

"The alt attribute does not represent advisory information. User agents must
not present the contents of the alt attribute in the same way as content of
the title attribute."

So, strictly speaking user agents could provide access to the alt text
somehow -- but not through a tooltip and not on-screen where the image
should go.  So it doesn't leave too many options and doesn't provide any
discussion of recommendations on providing this information to users.

> I agree that user agents that don't make longdesc available to all users
> all the time are not doing as well as they should. Putting requirements in
> specifications doesn't, by itself, change implementations. But I welcome
> input on strengthening the requirements...

Access to longdesc information in my opinion is more critical than alt text
because deciphering a descriptive meaning out of an image requires more
cognition and visual skill than abstracting the meaning from a simple image.

Jonathan

-----Original Message-----
From: Charles McCathie Nevile [mailto:chaals@yandex-team.ru]
Sent: Friday, March 29, 2013 12:13 PM
To: Frank M. Palinkas; David Woolley; Jonathan Avila
Cc: Mattingly, F Darrell; WAI Interest Group; Guettler, Karen M
Subject: longdesc requirements Re: alt tags for graphs

Hi Jonathan, all

On Fri, 29 Mar 2013 01:53:40 +0100, Jonathan Avila
<jon.avila@ssbbartgroup.com> wrote:

> [Frank wrote] FYG about @longdesc:

> I posted to the WCAG HTML Accessibility Taskforce list my thoughts on
> this

(do you have a pointer to that mail? I can't find it :( )

> - I'll briefly restate them here.

I'll reply here. But since there is a suggestion here to change the spec,
I'll also reply to your mail if I find it, or start a new thread on the
topic, in the HTML-a11y task force (which is the group formally producing
the spec).

> With the current proposal and previous requirements user agents were
> not and still are not required to expose longdesc to users or required
> to make it keyboard accessible.  It's indicated that "user agents"
> should make them keyboard accessible.

I'm not sure I understand. The requirements on user agents are:

User agents should make the link available to all users through the regular
user interface.
User agents should expose the link to relevant APIs, especially
accessibility-oriented APIs.
User agents should enable users to discover when images in a page contain a
long description.

Are you simply proposing that the "should" reqiurements be strengthened to
MUST? And that there should be a matching requirement to make them keyboard
accessible?

I would certainly be happy if the the shoulds listed become musts. If you
would like to raise a bug, please do, or I can do it if you prefer.

I don't think that the normative requirement to be keyboard-accessible
belongs in this spec - it is a general accessibility requirement for User
Agents that run on devices where keyboards can be used, so is in UAAG. I
would propose instead adding an informative note and a reference, if you
think it is necessary to make this particular point.

> This perpetuates the idea that alternatives are only needed for users
> who cannot see images or have images turned off.

It is certainly not my intention to perpetuate that idea, because I believe
it is wrong.

> The HTML specification in fact indicates that alt shall NOT be
> display when images are displayed as it acts a replacement for images.
> So it's not surprising the longdesc would follow down this same path
> as alt.

It would surprise me, as the person who wrote the text of the longdesc spec.
I would think the HTML spec is wrong to insist on that, and would not want
to follow. But I just read
http://www.w3.org/TR/html5/embedded-content-0.html#the-img-element (the
Candidate Recommenation draft) all the way through, and as far as I can tell
it doesn't have that requirement.

On a related note, I had an example in an early draft of a decorative image,
with a null alt attribute, but which used longdesc to provide a detailed
description for those who wanted it. This example was removed because a) it
was not necessary and b) it was in conflict with WCAG techniques.
Personally, I think the example is valid, and we should consider whether
there is a real conflict with WCAG techniques, and if so which is actually
correct.

> I have no problem with programmatically associating long description
> or long description links with an image but it MUST be available to
> all user groups without having to install special plug-ins or run
> assistive technology to access or make user agents display information
> that others can access without such requirements.

I agree that user agents that don't make longdesc available to all users all
the time are not doing as well as they should. Putting requirements in
specifications doesn't, by itself, change implementations. But I welcome
input on strengthening the requirements...

cheers

Chaals

--
Charles McCathie Nevile - Consultant (web standards) CTO Office, Yandex
       chaals@yandex-team.ru         Find more at http://yandex.com
Received on Monday, 1 April 2013 14:00:34 UTC

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