W3C home > Mailing lists > Public > public-html@w3.org > October 2009

Re: ISSUE-30 (Longdesc) Change Proposal

From: Charles McCathieNevile <chaals@opera.com>
Date: Thu, 29 Oct 2009 09:34:50 +0100
To: "Lachlan Hunt" <lachlan.hunt@lachy.id.au>, "Leif Halvard Silli" <xn--mlform-iua@xn--mlform-iua.no>
Cc: "public-html@w3.org" <public-html@w3.org>
Message-ID: <op.u2jzgcckwxe0ny@widsith.eng.oslo.osa>
On Tue, 27 Oct 2009 13:10:23 +0100, Lachlan Hunt  
<lachlan.hunt@lachy.id.au> wrote:

> Leif Halvard Silli wrote:
>>> On Mon, Oct 26, 2009 at 11:26 AM, Leif Halvard Silli
>>>> Another argument for this feature is, I think (as have been mentioned
>>>> earlier) that aria-describedby="" can be used for the same thing.
>>
>> I found Lachlan's comment in September: [1]
>>
>>> That would just be reinventing longdesc with a different name without
>>> solving any of the problems that longdesc has.
>>
>> However, upon rereading, it seems like Lachlan was actually expressing
>> satisfaction that describedby and longdesc has not been defined the same
>> way. There are other comments in that same thread expressing similar
>> things.
>
> My take on longdesc is that it's badly designed for the problem it's  
> trying to solve, and even aria-describedby is not ideal for addressing  
> the cases where the description is in an external document.

Hmmm. I think longdesc wasn't a perfect solution, and aria-describedby  
isn't either (as currently specified, but it's only in draft so that can  
be changed).

> I would rather see the problem of how to provide access to a long  
> description in an external document addressed in a way that can utilise  
> ordinary links, without introducing too much complexity.  There are  
> several ways this could be achieved.
>
> 1. Making the image itself a link to its description:
>
> <a href="desc.html" rel="longdesc"><img src="image" alt="..."></a>
>
> The rel=longdesc attribute should be enough for ATs to identify the link  
> as being a long description, and the fact that the image is inside the  
> link should be enough to make the association.

This fails for the very common case where an image is already a link to  
something. One of the things longdesc is useful for is the case where  
someone says to their friends (as you do) "click on the picture of a  
little man in green facing left".

> 2. If the image has a caption, including the link within that:
>
> <figure>
>    <img src="image" alt="...">
>    <legend>Some caption here.  <a href="desc.html" rel="longdesc">More  
> information</a>.</legend>
> </figure>

Yep, where there is a caption then longdesc is not so necessary (although  
the explicit association of the image and its description is lost, since  
the caption may equally be pointing to something completely different).

Note also that "more information" as a link is explicitly recommended  
AGAINST in accessibility, precisely because it is not clear to real users  
what the information will be about (this is due to the way that blind  
people in particular actually use web browsers, a pattern of learned  
behaviour that has been established over a couple of decades and strongly  
reinforced by implementations over that time).

> 3. Using an adjacent link that shares the same parent as the image  
> itself, and implying the association:
>
> <p><img src="image" alt="..."> <a href="desc.html" rel="longdesc">More  
> information</a></p>
>
> This would need to have an implicit association algorithm defined to  
> handle cases where there are more than one image and/or description  
> links.

It also requires explicit text to be added to the page, something that  
often fails real world requirements.

So longdesc is not a solution to all problems, and often not necessary,  
but none of these solutions apply to the case where it is most necessary.

cheers

Chaals

-- 
Charles McCathieNevile  Opera Software, Standards Group
     je parle français -- hablo español -- jeg lærer norsk
http://my.opera.com/chaals       Try Opera: http://www.opera.com
Received on Thursday, 29 October 2009 08:35:31 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Wednesday, 9 May 2012 00:16:51 GMT