Re: HTML Action Item 54 - ...draft text for HTML 5 spec to require producers/authors to include @alt on img elements.

>Defining any content produced by the use case to be non-conforming is
not >handling the use case, at least for purposes of document
conformance.

That is your opinion, others including myself think otherwise.

re your example:
"<p id="info">Complete explanation of a chart with full details.</p>
<img src="chart.png" alt="Explanation of chart." aria-describedby="info">"

The user may also access it like this:

"Complete explanation of a chart with full details". if they skim read

or

"Explanation of chart". or this if they navigate by graphics or they
are using a magnifier/reader which will read content under the mouse
cursor.

Problem with your argument is you do not take into account the
different mechanisms used by people with disabilities to interact with
content. It is not purely linear or a matter of whole blocks of
content being voiced.

You playing around with voiceover and then basing arguments upon your
observations, is not a sound basis for much at all.

> That sounds like an appeal to authority, not a justification. Even the best
> exerts make mistakes, or fail to think through certain edge cases. Or
> sometimes, they can reach correct conclusions that non-experts find
> surprising, in which case an explanation can be of great benefit.



Not appeal to authority, nor a justification, but a recognition that a
group of people have spent a lot of time working on the guidelines,to
provide benefits for people with disabilities. Their priority has been
people with disabilities, not browser vendors or authoring tool
vendors or authors. So I  trust their advice about what makes an
appropriate text alternative over your intuitive fumblings.

 As i said before talk to the people who developed WCAG 2.0 if you disagree.

see ya!

On 12/05/2008, Maciej Stachowiak <mjs@apple.com> wrote:
>
> On May 12, 2008, at 5:57 AM, Steven Faulkner wrote:
>
> > Hi Maciej,
> >
> >
> > > This proposal does not cover the use case
> > > where HTML generated by a tool does not have a textual alternative
> > > available.
> > >
> >
> > The current draft of item54 does not provide explicit coverage, as stated:
> >
> > 'Advice has been sought, is needed, and is pending from PFWG regarding
> > the separate issue of what an authoring or publishing tool should
> > insert, in a case where no alt has been provided by the author, but
> > the image is known to be "critical content".'
> >
> > source: http://www.paciellogroup.com/blog/misc/uc/
> >
> > But, the proposal does implicitly cover the use case (the content will be
> > invalid, because the author is either using a broken authoring tool,
> > or doesn't care about the structure of the data).
> >
>
> Defining any content produced by the use case to be non-conforming is not
> handling the use case, at least for purposes of document conformance.
>
> >
> >
> >
> >
> >
> > > It also requires redundant text in many cases where the current spec
> would
> > > call for empty alt.
> > >
> >
> > The current spec conflicts with WCGA 2.0 (candidate recommendation)
> > advice on such images.
> >
> > As stated in the proposal;
> > "The aim of this draft is therefore to comply with WCAG 2.0, Guideline
> > 1.1. Text Alternatives:"
> >
> > source: http://www.paciellogroup.com/blog/misc/uc/
> >
> >
> > > Is there any reason to believe that redundant text description of an
> image
> > > that recapitulates the text is helpful, rather than harmful, to users
> who
> > > use textual alternatives?
> > >
> >
> >
> > potential benficiaries of this information include, blind users,
> > visually impaired users, cognitively impaired users and user with
> > intellectual disabilities. each of the user groups have different
> > needs and AT that they use will consume and present the information in
> > a variety of ways, users are also provided with a wide variety of
> > options on how to navigate and access content.
> >
>
> I believe my question is valid regardless of the target audiences and their
> many options.
>
> > So your simplistic notion of redundancy does not hold up.
> >
> > examples:
> > A screen reader user may initially hear the short summary of the image
> > content, then access then access the longer description via a key
> > stroke.
> >
> > The screen magnifier/reader user who can see the image, but not
> > understand its contents due to it being to blurred, will have the alt
> > text announced, to give them some idea of the image content.
> >
> > The cognitively impaired user accessing the page using a talking
> > browser, likewise will have the benefit of a short image label,
> > although they may not be able to understand the content of the image
> > from its visual rendering.
> >
> > for all of these users the presence of the short alt text provides an
> > alternative labelling mechanism that can be presented to the user via
> > their AT.
> >
> > For the magnifier user, the short text alternative may or may not be
> > provided visually. The association between the aria-describedby text
> > and image could be rendered visually in a number of of ways.
> >
> > Different AT's currently provide different mechanisms to navigate and
> > access content. For example screen readers such as JAWS provides
> > methods to navigate a page via graphics (using the G key), in this
> > case, not providing the alt text means that the image would be
> > skipped.
> >
>
> Thank you for the explanation of how different users may interact with
> assistive technologies. However, that does not answer my question. In the
> part of the proposal I cited, the suggested markup structure was more or
> less like this:
>
> <p id="info">Complete explanation of a chart with full details.</p>
> <img src="chart.png" alt="Explanation of chart." aria-describedby="info">
>
> A user reading this document with a screen reader would hear something like
> this, as they navigate:
>
> "Complete explanation of a chart with full details."
> "Image. Explanation of chart. Long description available"
>
> Then, if the user chooses to hear the long description:
>
> "Complete explanation of a chart with full details."
>
> Can you explain why this is better than hearing "Complete explanation of a
> chart with full details" once, and then skipping the image (which is what
> would happen if the image had alt="" and no aria-describedby attribute)? I
> tried it with VoiceOver on Mac OS X, and the repetition does not seem
> helpful.
>
> >
> > > Is there reason to believe that screen reader users like to hear things
> two
> > > or three times? I have not done any studies but this is surprising to my
> > > intuition. I would have concluded that using alt="" to present the
> screen
> > > reader user (or other users of aural or text-only media) with the
> > > information only once is best. It may be that this surprising conclusion
> is
> > > correct but I would like to hear some justification.
> > >
> >
> >
> > As stated previously
> >
> > "The aim of this draft is therefore to comply with WCAG 2.0, Guideline
> > 1.1. Text Alternatives:"
> >
> > The advice in WCAG 2.0 has been developed over a long period of public
> > consultation. If you feel that your view of what constitutes best
> > advice on how to provide appropriate text alternatives is superior to
> > WCAG,  I urge you to correspond with the WAI WCAG working group. I am
> > sure that they would be more than happy to explain how they arrived at
> > the advice provided in WCAG 2.0.
> >
>
>
> That sounds like an appeal to authority, not a justification. Even the best
> exerts make mistakes, or fail to think through certain edge cases. Or
> sometimes, they can reach correct conclusions that non-experts find
> surprising, in which case an explanation can be of great benefit.
>
> Regards,
> Maciej
>
>
>


-- 
with regards

Steve Faulkner
Technical Director - TPG Europe
Director - Web Accessibility Tools Consortium

www.paciellogroup.com | www.wat-c.org
Web Accessibility Toolbar -
http://www.paciellogroup.com/resources/wat-ie-about.html

Received on Monday, 12 May 2008 15:59:58 UTC