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Re: LONGDESC: some current problems and a proposed solution added to the wiki

From: Thomas Broyer <t.broyer@gmail.com>
Date: Sat, 30 Jun 2007 12:47:24 +0200
Message-ID: <a9699fd20706300347y50379c73i650b1cb91b97d875@mail.gmail.com>
To: public-html@w3.org
2007/6/30, Peter Krantz:
>
> Problems with the current longdesc method:
>
> - Assistive devices need to make an extra HTTP request to retrieve the
> content. A risk for availability problems.
> - It is unclear how the web page containing the extended description
> should look. If it includes the web site navigation toolbars and
> headers it increases the time to reach the content for the user.
> - It is difficult to script usage of the extended content to e.g.
> display it in a popup when hovering the image.
> - Search engines need to make an extra request to get information
> about the image.
> - Forcing the user to navigate to a separate page increase the risk
> for usability problems (do they know they can click the image?).

That's not true if you use a self-document reference.

> Proposal
>
> If research shows that longdesc usage is limited, now is a good time
> to change the markup. Eric Eggert's suggestion makes sense but there
> should be a connection with the image to enable programmatic discovery
> and manipulation of the extended description text. As we should strive
> for backwards compatibility I suggest the following.
>
>     * longdesc attribute of the ig element is removed
>     * the role attribute is used to identify a longdesc
>     * the for attribute is used to connect the extended description to
> a particular image
>
> An example:
>
> <img src="/flag.gif" id="ukflag" alt="">
>
> ...
>
> <div role="longdesc" for="ukflag">
>   <p>The Flag of Union has been the official flag of the United
> Kingdom since the Act of Union of 1807, which created the modern
> political entity known as the United Kingdom, which, this year,
> celebrates its 200th anniversary.</p>
>   <ul>
>       <li>[Whatever]...</li>
>   </ul>
> </div>

How is this that different from:

<img src="/flag.gif" longdesc="#ukflag">

...

<div id="ukflag">
 <p>The Flag of Union has been the official flag of the United
Kingdom since the Act of Union of 1807, which created the modern
political entity known as the United Kingdom, which, this year,
celebrates its 200th anniversary.</p>
 <ul>
     <li>[Whatever]...</li>
 </ul>
</div>

> This method has the following advantages:
>
>    1. Backwards compatible with HTML 4. Current UA:s will render the content.
>    2. Easier for assistive devices to parse and present extended
> description in a different context.
>    3. Better usability. Extended description is available without the
> need to navigate to a new page that may repeat navigation and header
> markup.
>    4. Scriptability/stylability. Extended content div can e.g. be
> hidden and displayed on mouseover or whatever the designer wants.
>    5. Easy to add this markup to existing web pages. An editor only
> needs to wrap the existing description in a div like above to increase
> accessibility.

All this is already true if you use a self-document reference.

Just my 2 c€nts, not advocating anything (I do not have a strong
opinion on longdesc)

-- 
Thomas Broyer
Received on Saturday, 30 June 2007 10:47:38 UTC

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