Re: IMG ALT attribute in HTML 4.0

Dave Raggett (dsr@w3.org)
Wed, 10 Sep 1997 10:48:50 -0400 ()


Date: Wed, 10 Sep 1997 10:48:50 -0400 ()
From: Dave Raggett <dsr@w3.org>
To: Liam Quinn <liam@htmlhelp.com>
cc: Jukka Korpela <jkorpela@cc.hut.fi>, www-html@w3.org
In-Reply-To: <3.0.3.32.19970910100233.008d7e60@undergrad.math.uwaterloo.ca>
Message-ID: <Pine.WNT.3.95.970910101134.-174449D-100000@hazel.hpl.hp.com>
Subject: Re: IMG ALT attribute in HTML 4.0

On Wed, 10 Sep 1997, Liam Quinn wrote:
 
> Again, TITLE seems appropriate for a short description and
> LONGDESC for a long description.  What seems odd in the DTD at
> <http://www.w3.org/MarkUp/Cougar/Cougar.dtd> is that the LONGDESC
> attribute was added to IMG but not to OBJECT.  Is this just an
> oversight? 

The discussion in the HTML working group on long descriptions
shifted from LONGDESC to making sure that image maps are supported
for OBJECT. With agreement on image maps for OBJECT, the LONGDESC
attribute will disappear from IMG unless there is agreement that we
still need it. 

How would authors use OBJECT and IMG to provide accessible pages
bearing in mind the likelihood that many people will be browsing
the Web for a long time to come using browsers that don't support
OBJECT, let alone shapes.

One approach is to use IMG with the alt attribute and client-side
image maps. This is well supported but doesn't allow authors to
provide long descriptions with rich text.

 Approach A:

  <IMG src=map.gif usemap="#flavors" alt="Ice cream flavors:">
  <MAP name="flavors">
    <AREA alt="Vanilla" shape=poly coords="..." href=...>
    <AREA alt="Chocolate" shape=poly coords="..." href=...>
    ...
  </MAP>

Another approach is to use OBJECT with the shapes attribute.  The
OBJECT element then contains a rich text description with hypertext
links that double up to define hotzones on the image.  This is the
preferred long term solution.  Browsers that don't support OBJECT
don't render the image and only show the textual description. 

 Approach B:

  <OBJECT data=map.gif shapes>
    <P>We offer a full range of ice creams including:
    <A shape=poly coords="..." href=...>Vanilla</a>,
    <A shape=poly coords="..." href=...>Chocolate</a>,
    ...
  </OBJECT>

You could place the IMG and MAP elements within the OBJECT
element, but this doesn't really solve anything.

Perhaps this doesn't matter - perhaps we should just go all out to
encourage people to upgrade to browsers that support OBJECT with
shapes, e.g. for the 5.0 round of browsers from the big two. I like
this approach - but can we get enough content providers to support
it? 

The new feature is not wonderfully backwards compatible.
Authors can't provide good graphics on old and new browsers
whilst at the same time providing rich text descriptions.
There are two solutions as far as I can see:

  a) use a tool to generate different versions of HTML
     for delivery to browsers according to the user agent.

  b) add LONGDESC to IMG

If the 5.0 browsers from the big two support OBJECT shapes
and enough people upgrade quickly, then perhaps authors will
be happy enough to start using it. In the meantime authors
will be adding to the enormous number of Web pages that provide
a poor experience to people with text-only browsers.

So should the HTML 4.0 spec include LONGDESC or should we
just rely on OBJECT shapes and encourage content providers
to exploit the user agent header?

Regards,

-- Dave Raggett <dsr@w3.org> http://www.w3.org/People/Raggett
phone: +44 122 578 2521 (office) +44 385 320 444 (gsm mobile)
World Wide Web Consortium (on assignment from HP Labs)