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Re: Investigating the proposed alt attribute recommendations in HTML 5

From: David Poehlman <david.poehlman@handsontechnologeyes.com>
Date: Tue, 11 Sep 2007 17:04:15 -0400
Message-ID: <006001c7f4b7$50a21320$0601a8c0@HANDS>
To: "Henri Sivonen" <hsivonen@iki.fi>, "Steve Faulkner" <sfaulkner@paciellogroup.com>
Cc: "HTMLWG" <public-html@w3.org>, <wai-xtech@w3.org>

Headings, lists and tables are aNo matter what we do we will never convince 
some of the importance of valid or proper code unless we find some way of 
preventing the code from being produced which we are sure not to do.  As 
with tables, headings and lists, I doubt developping a database will solve 
this issue.
s poorly used as alt is and the solution os to provide a good spec that au 
and ua can follow.
----- Original Message ----- 
From: "Henri Sivonen" <hsivonen@iki.fi>
To: "Steve Faulkner" <sfaulkner@paciellogroup.com>
Cc: "HTMLWG" <public-html@w3.org>; <wai-xtech@w3.org>
Sent: Tuesday, September 11, 2007 9:34 AM
Subject: Re: Investigating the proposed alt attribute recommendations in 
HTML 5



On Sep 11, 2007, at 13:58, Steve Faulkner wrote:

>> That behavior is that alt='' suppresses
>> the image altogether but the omission of the attribute causes a
>> bearable placeholder to be presented so that the user knows that
>> there's an image.
>>
> The problem with this is that there is no way for the software to
> know whether the images presence needs to be announced to the user.

Hence, the need for the announcement to be bearable.

> for example in the cases of decorative images or layout images
> without an alt attribute how are these to be filtered out from
> images that contain "critical content" without an alt attribute.
> What is clear (to me) is that using the omission of the alt
> attribute is not and will not be a sufficent flag to assitve tech.

The problem with any "reliable "flag is that it can be auto-generated
just to pass validation.

> Currently something like 30% (not sure of the exact stats) of
> images on the web do not have alt attributes, of these how is the
> assistive tech to discern which are worthy of announcing to a user
> and which are to be safely ignored?

With existing content, explicit annotation won't be available
regardless of what this WG does. I suggest considering various
characteristics of image files (dimensions, format, spikiness of
color distribution histogram, etc.) that can be extracted in
software, taking a large sample of Web images, asking humans to
classify the images into announcable and non-announcable and feeding
the data into a Bayesian classifier. I'm pretty sure a probabilistic
classifier could tell which images are non-decorative photos, which
are thumbnails and which images have the traits of standard-size ad.
Telling apart UI icons and small decoration might be harder.

> One suggestion has been to provide a noalt attribute I am as yet
> unsure of the merits of this proposal. Another suggestion would be
> to require the alt unless the image has meta data explicitly
> associated with it in some other way. I also asked the question on
> the list ( http://lists.w3.org/Archives/Public/public-html/2007Sep/
> 0150.html) whether alt=" " (quote space quote) could be used to
> flag images that should have an alt text but none is supplied.

Considering JAWS, alt=' ' degrading into alt='' may be a better
backwards compatibility story than noalt degrading into no alt. Is
there any single ASCII punctuation character that could be used to
denote announcable but altless image and that would have a reasonable
degradation story in current screen readers? (To make the current
screen readers say something and to have something that is visible to
sighted authors looking at the source.)
>> it is clear that the current state of JAWS is so bad
> I don't know what you would expect a screen reader to do?

Examples in
http://lists.w3.org/Archives/Public/public-html/2007Sep/0283.html

-- 
Henri Sivonen
hsivonen@iki.fi
http://hsivonen.iki.fi/
Received on Tuesday, 11 September 2007 21:04:27 GMT

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