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DESC discussion

From: Al Gilman <asgilman@access.digex.net>
Date: Thu, 16 Oct 1997 13:25:30 -0400 (EDT)
Message-Id: <199710161725.NAA27887@access2.digex.net>
To: w3c-wai-ig@w3.org

DESC      Text associated with images


Images are very important to the look of most Web pages.  This
naturally presents accessibility problems for people with visual
disabilities. Traditionally images in HTML pages are specified
using the IMG element, and to a lesser extent with the form field
INPUT element for image fields (type=image).

For both of these elements, authors can provide a short
description with the attribute named "alt". Most authoring
guidelines recommend authors to use this feature. HTML 4.0 makes
this a required attribute.

What's missing is an ability to specify a longer rich text
description for images -- a richer description that can include
headings, paragraphs, lists and hypertext links etc.  This is
especially critical for images that are being used for image

Also in this proposal, we're addressing the need for FRAME and for
generated ALT text to be identified.


HTML 4.0 introduces a new element named "object" for embedding
images and other objects into HTML pages. Unlike IMG, object
is a container that wraps around the alternative content to
be used when the object itself can't be rendered directly.
We are hoping that authors will switch from IMG to OBJECT over
a period of time.

Many people take a long time to upgrade to newer browsers. As a
result, Websites design their HTML pages to look good on older
browsers as well as the latest models.  The OBJECT element is
not upward-compatible with the behavior of existing browsers.

As a result, the IMG element will be in use for a long time to
come, and we still need to find a way for authors to make IMG
more accessible. The proposed solution is to add a new attribute
named "longdesc" that can be used to provide a URL pointing to a
longer description. This will in most cases be placed in a
separate file. People using say speech-based browsers will first
read the alt attribute and then choose whether to follow the link
provided by the longdesc attribute.

In addition, the TITLE and LONGDESC attributes should be possible
on FRAME and IFRAME elements, because these elements are often
images or graphical layouts benefiting from a text alternative
and/or explanation.

We would like to refine the OBJECT processing rules in the HTML4 spec
as follow:

 If the content of OBJECT is not another OBJECT element, then the
 following rules apply:
 (1)  if SHAPES is specified, a visual user agent (with graphics enabled) 
 must search the content of OBJECT for anchors with COORDS attributes,
 which define the areas of the image map. In all other circumstances,
 visual user agents (with graphics enabled) should ignore the content of
 object.  (2) Non-visual user agents, (or visual user agents with graphics
 disabled) must always render the content of OBJECT.

Additionally, we think the note on generating ALT text automatically:


should be improved to say that some prefix will be added to the
generated alt text when the author is not responsible for it, so that
the user know what quality to expect.

We also think this section should be moved in the Browser guideline
book, not in the HTML spec.


Here are sample questions the Interest Group might want to raise
and answer.

Can an IMG have both a USEMAP and a LONGDESC?  What would you use
this combination for, and how should this be handled by browsers?

What are the pros and cons of putting a LONGDESC on an IMG versus
hard-coding a link to the description in the page?


Please discuss this issue by sending email to w3c-wai-ig@w3.org .
Include the symbol DESC in the subject heading of your message,
to help other subscribers organize the volume of mail we hope
this will generate.
Received on Thursday, 16 October 1997 13:25:54 UTC

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