W3C home > Mailing lists > Public > w3c-wai-gl@w3.org > January to March 2004

RE: [1.1] Text-equivalents for illustrations?

From: Gregg Vanderheiden <gv@trace.wisc.edu>
Date: Sun, 14 Mar 2004 21:17:59 -0600
To: "'Yvette P. Hoitink'" <y.p.hoitink@heritas.nl>, w3c-wai-gl@w3.org
Message-id: <0HUL00DMUL6JQW@smtp3.doit.wisc.edu>

Good comments.

Here are some random musings as I wait for a delayed plane

NOTE: The following are just some comments from me -- not in any way an
official finding of the group.
I think we again have to go back to function.

As I understand it... 

If the function of the dotted line you mentioned is to divide two blocks of
text -- then it does need an alt text and the alt text should be "divider
line"  or some such.   It should not describe what the line looks like
('e.g. dotted line") but rather its function.

If a graphic is on the page to confirm to the viewer that they got to the
right page...  and the page already has a title -- then it may not have an
additional function.  But if it is to show how nice a place it is -- then it
does have a function - and that function should be provided in text.   You
do not need to describe every little detail in the picture.  (e.g. if it is
a picture of the town you don't have to describe the number of buildings,
what they look like, the street sign, etc. etc. unless some part of that is
critical to the function of the town.   E.g.  could any other picture of
another part of the town have been used instead.) 

In general I would think the safer thing to do is to provide short alt text
of pictures rather than decide that they have no function.   It is rarely
true.     I would ask, why is this picture here.  Could I put any other
random picture here?  If not, why not.   Why is it important to use this
picture vs a random picture.  What is it conveying.


 -- ------------------------------ 
Gregg C Vanderheiden Ph.D. 
Professor - Ind. Engr. & BioMed Engr.
Director - Trace R & D Center 
University of Wisconsin-Madison 

-----Original Message-----
From: w3c-wai-gl-request@w3.org [mailto:w3c-wai-gl-request@w3.org] On Behalf
Of Yvette P. Hoitink
Sent: Sunday, March 14, 2004 3:33 PM
To: w3c-wai-gl@w3.org
Subject: [1.1] Text-equivalents for illustrations?

Hello everyone,

I posted a link to the working draft on a Dutch webdesign newsgroup. We got
to talk about the need for a text equivalent for non-text content. Two
extremes are clear: If you illustrate a principle using an image, you have
to provide a text equivalent. If you use an image as a spacer image to force
the layout, it needs a null equivalent (alt="" in HTML). But what about
images that are used as an illustration but could be described in words?

The case we discussed was the largest image on
http://www.erfgoedoverijssel.nl, a website my company built last year about
the local history of a village called Denekamp. The alt-text for the largest
image currently says "Photograph of the backside of the Keizer house with
the Saint Nicholas church in the background". Both the Keizer house and the
Nicholas church are familiar buildings in Denekamp, so both the picture and
the alt give a 'Denekamp' feeling to the site for people who are familiar
there (which is why these illustrations were chosen). 

One people in the discussion group said he thought this image should have a
null alt, because adding this text didn't help accessibility since the
function of the image is purely decorative. I disagree because I do not want
to decide for a blind person that he doesn't need or want this information.
Also, people who can't see very well and use screenreaders can decide based
on the alt if they want to take the trouble to view the image. Giving it a
null alt means people without visual browsers do not know what they're
missing. One comment was of the group was: blind people have already
accepted that they can't see the images, now I need to accept that as well. 

One person in the newsgroup had a nice litmus test to determine whether you
need an alt or a null alt: If the words of the potential text equivalent
appear in the text and are illustrated by the image, a null alt suffices. If
the content of the image is not discussed in the text you have to wonder
what the image is doing there in the first place. The answer to that
question decides whether you need an alt or not. If it is just an
illustration, a null alt is enough.

Bottom line: In WCAG 2 we seem to require text equivalents for practically
anything you can put into words. But does that help accessibility? I can
describe a dashed line in words but that only annoys people instead of
helping them. I think we need to think about illustrations whose function is
purely decorative. I don't think they fall in the category "Non-text content
that is designed to create a specific sensory experience" so according to
the current formulation it would require a text equivalent. But are we sure
we're helping people when doing that?

Yvette Hoitink
Heritas, Enschede, The Netherlands
Received on Sunday, 14 March 2004 22:18:31 UTC

This archive was generated by hypermail 2.4.0 : Thursday, 24 March 2022 21:07:33 UTC