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RE: Is longdesc a good solution? (was: Acessibility of <audio> and <video>)

From: John Foliot <foliot@wats.ca>
Date: Sun, 7 Sep 2008 17:59:08 -0700
To: "'Lachlan Hunt'" <lachlan.hunt@lachy.id.au>, <wai-xtech@w3.org>
Cc: <public-html@w3.org>, "'W3C WAI-XTECH'" <wai-xtech@w3.org>
Message-ID: <00fd01c9114e$19f92750$863c42ab@stanford.edu>

Lachlan Hunt wrote:

> It has been suggested to me that there may be cases where an image
> needs 
> to have a description and provide a link elsewhere, which would make
> this solution unusable. But no-one has yet been able to provide a
> valid 
> use case illustrating that.

OK, here you go: http://www.nasa.gov/

The main page has a picture of the shuttle Atlantis, with the not so great
alt text of "STS-125 Atlantis". However, the photo is actually quite
complex, and so could benefit from a longdesc (although sadly it does not
exist).  Clicking on the image takes you to the section or the Nasa site
concerning the Atlantis shuttle. 

Now if we cleaned up the alt text to read: "photos of the STS-125 Atlantis
space shuttle on the launch pad" that would probably be sufficient
alternative text for many or most users. The last thing we want to do here
however is overload the alt value with a paragraph's worth of text, as this
much verbosity becomes an hindrance rather than a help, a fact confirmed by
many daily screen reader users (and if you are a daily screen reader using
this and agree, please respond affirmatively or negatively if you disagree).
Brevity in @alt is always appropriate - the text needs to be succinct.
Screen Readers would then be signaled both the alt text, as well as the fact
that the image is a link.  

However a fuller description of the photo would also reveal/announce that
there is actually two shots of the shuttle, one a close up on the launch
pad, the other an ariel photo of the launch pad rolling to the launch
position, with a copy of the mission emblem separating the two photos.
Further, a description of the emblem would probably be in order: a tall oval
patch with a black background.  A representation of the Hubble telescope
sits at the bottom, with a blue, V shaped cone emerging from the top,
representing the view of the telescope; this blue cone contains white
abstract stars and planets.  Also present on the patch is a representation
of the shuttle itself, located in the lower right side, with a red trail
behind it.  Finally the names of the mission members encircle the patch,
along with the mission number of 125 in the lower left corner. 

The problem however is that you could not simply turn the image into a link
to this expanded description, as an anchor element already exists to the
Shuttle section of the site.  How then do you provide linkage to the longer
description, but unobtrusively - no [D] links or "in-the-clear" text links
are permitted, and you cannot change the visual layout of the page at all.
This is where @longdesc comes to play.

I have spent very little time with this (near zero actually), and lack the
cycles today to re-work this into a usable demonstration of what I am
talking about.  However the amount of information that would go into the
longer description is too verbose for @alt, and the design does not allow
for an in-page rendering of the longer description, so it must be stored off
page (especially since there are other equally complex images on the page)

So... If not @longdesc how would you solve the problem I described for this
page?  You asked for a real use-case, and there you have one.  The fact that
the developer did not work this up is an admitted problem, but if he/she
were to be called out on Monday to fix this, how would you counsel them?

JF
Received on Monday, 8 September 2008 00:59:48 UTC

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