W3C home > Mailing lists > Public > public-html@w3.org > July 2007

Re: unifying alternate content across embedded content element types

From: Charles McCathieNevile <chaals@opera.com>
Date: Sun, 15 Jul 2007 18:19:23 +0900
To: "Robert Burns" <rob@robburns.com>, "Patrick Garies" <pgaries@fastmail.us>
Cc: public-html@w3.org
Message-ID: <op.tvh1ilqtwxe0ny@widsith.local>

On Sun, 15 Jul 2007 17:06:41 +0900, Robert Burns <rob@robburns.com> wrote:


> To take out one of your examples:
>> Code: <img alt="?" src="cat.png">
>> Code <p>I let my cat, Fluffy, played with a ball of yarn when we were  
>> at my friend’s house a year ago. He seemed to enjoy it.</p>
>
> My contention (and this was a point I think Jon was making too), is that  
> when a textual equivalent describing the image is already in the  
> surrounding  prose, it shouldn't be repeated for the @alt attribute. My  
> proposal was something shorter that let's the user know what meaning the  
> image conveys in a way that matches it with the prose available to all  
> users.
>
> I suppose an alternative could be:
>> Code: <img alt="Fluffy with the ball of yarn" longdesc='#fluffyplays'  
>> src="cat.png">
>> Code <p id='fluffyplays' >I let my cat, Fluffy, played with a ball of  
>> yarn when we were at my friend’s house a year ago. He seemed to enjoy  
>> it.</p>
...

In both the above cases, a lot of accessibility people would advise  
(correctly, IMHO) that you should have alt="" signifying that there isn't  
anything you *need* to replace the image.

The longdesc in the second example (and a putative one in the first  
example that points to some other content describing fluffy and the yarn)  
provides the clue that a user needs to know there was an image so they can  
know there is more description should they desire it. (Configuration might  
be different for internal and external references, so that in the second  
example longdesc by default is suppressed, unless the user asks for a more  
informative view of the page).

>> Image: icon depicting a house
>> Bad Example: <a href="/"><img alt="House Icon" src="home.png"></a>
>> Good Example: <a href="/"><img alt="Go to the Home Page"  
>> src="home.png"></a>

Indeed. Idiomatically in english, this might just be alt="home", in french  
it is more likely to be "accueil" (reception), and in spanish "pagina  
principal".

The key to alt is not what the image looks like, but what you would put  
there if there were no image. And the normal design ideas about avoiding  
redundancy, maintaining consistency, and so on apply to text as well,  
although some of the specifics are slightly different. Think about flow  
and identifying terms as equivalent to having images that have clear  
borders against those that vaguely merge into the background for some  
qualitative idea of what I mean.

(Longdesc is about the appearance of the image. How do you recognise what  
someone describes as "the thing that is vaguely shaped like a squashed  
african war mask - some designer apparently figured that would conjure up  
the idea of home", or how do you realise that this is a caricature of the  
Mona Lisa, with a beer, cigarette, and her hair in curlers, rather than  
the real real thing - and would you recognise it again next time?. One of  
the nice things about having longdesc as an external reference is that you  
can re-use and cache it across different usage of the same image).

cheers

Chaals

-- 
   Charles McCathieNevile, Opera Software: Standards Group
   hablo español  -  je parle français  -  jeg lærer norsk
chaals@opera.com    Catch up: Speed Dial   http://opera.com
Received on Sunday, 15 July 2007 09:19:43 UTC

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