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

From: James Craig <jcraig@apple.com>
Date: Sun, 7 Sep 2008 18:56:45 -0700
To: John Foliot <foliot@wats.ca>
Message-Id: <17E7F546-45E3-4AA2-BA17-5B4F6ADEC0A2@apple.com>
Cc: Lachlan Hunt <lachlan.hunt@lachy.id.au>, wai-xtech@w3.org, public-html@w3.org

John Foliot wrote:

> 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.

In this case, no long description is needed. Certainly better alt text  
should be there, but the point of the image is adequately described by  
the title ("Shuttle Atlantis at the Launch Pad, Set for Hubble  
Mission") and the caption ("Atlantis' crew, targeted to launch on Oct.  
10, will upgrade the Hubble Space Telescope, extending the life of the  
groundbreaking observatory. [link] Hubble Servicing Mission, [link]  
Space Shuttle Section").

It is irrelevant that the image contains two photos from different  
perspectives and a graphic of the mission patch. It some respects, it  
may even be considered a decorative image. All three of those main  
sections contain large images that are intended to get the viewer to  
click through to the related article, the images are not there for  
their own sake.

Sometimes overly-detailed accessibility is championed at the expense  
of usable accessibility. Consider how often you "skim" content  
sections. Blind people don't want to be bogged down by minutia any  
more than sighted users do.

When @longdesc was the best solution, I argued that it should only  
rarely be used, specifically in the case of charts and graphs, where  
data visualization represents real page content that requires a longer  
explanation than @alt will allow.

Even image galleries (such as Flickr or a museum website) should  
rarely, if ever use longdesc. Yes, the main point of the content is  
the image itself, but that content should be described on the page. In  
the case of artwork, this usually provides benefit to non-disabled  
users, too. Imagine an image's in-page, visible long description  
provides detailed discussion of the artist's intention in his choice  
of color, and the form contrast or dynamic angular motion of the  
painting.

This kind of detail enlightens all viewers, and it doesn't need to be  
visible by default. The web comic, Penny Arcade (It may have been a  
different comic), used to have a drop-down section of the page that  
had a data table listing characteristics of each pane, including which  
characters were visible, the dialog, and any background information  
including links to events or jokes in previous strips that may have  
been missed by anyone but a regular reader. Though not initially  
visible, this information was useful for numerous reasons.

1. It increased the accessibility for blind readership.
2. I, for example, didn't know most of the character's names, so I  
could learn them by looking in the "long description" section.
3. Google could more accurately index the content of each page, so  
people could search for content by a phrase they remembered.
4. etc.

All without the use of longdesc.

The "Visual Complexity" gallery <http://www.visualcomplexity.com/vc/>  
has loads of examples where, in its original context, each graph or  
chart should probably have had used longdesc. On the VC site however,  
even though the images are charts and graphs, longdesc is not required  
because each item's page discusses the artistic data visualization  
technique used, and in the context of the gallery, the detail of the  
data itself is irrelevant.

James
Received on Monday, 8 September 2008 01:57:29 UTC

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