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longdesc semantics and optional content Re: unifying alternate ...

From: Charles McCathieNevile <chaals@opera.com>
Date: Sun, 15 Jul 2007 18:50:20 +0900
To: "Robert Burns" <rob@robburns.com>
Cc: "Gregory J.Rosmaita" <oedipus@hicom.net>, public-html@w3.org, "Andrew Sidwell" <takkaria@gmail.com>
Message-ID: <op.tvh2x6towxe0ny@widsith.local>

On Sun, 15 Jul 2007 17:32:57 +0900, Robert Burns <rob@robburns.com> wrote:

> On Jul 15, 2007, at 2:45 AM, Charles McCathieNevile wrote:
>
>>
>> On Sun, 15 Jul 2007 04:35:01 +0900, Robert Burns <rob@robburns.com>  
>> wrote:
>>
>>> On Jul 14, 2007, at 10:30 AM, Gregory J. Rosmaita wrote:
>>
>>>> so, yes, ALT and LONGDESC serve 2 distinct purposes...

>> Hmmm. I actually think if the content as matching alt, but having a  
>> little more flexibility. Although you can put in a link to stuff that  
>> might be useful but might be superfluous (which is what longdesc gives)  
>> you don't have the defined semantics that you do with longdesc.
>
> I'm sensing this may be important to my understanding some of the  
> disagreement. If the contents of an <object> element are viewed more  
> like the semantics of the @alt attribute than, that's a very different  
> use for those contents than I ascribe to them. The thing I like about  
> the <object> element is its ability to contain a very semantically  
> (markup) rich alternate equivalent fallback description of the embedded  
> content. ... Or rely on the fact that a user can stop a screen reader at  
> any time so the contents can simply serve that role.
>
> However, I'm not clear what you mean when you say: "you don't have the  
> defined semantics that you do with longdesc"

As a user, you may not really want the full and detailed description of  
the image of Cook at Botany Bay - especially when it is somewhat  
tangential to the fundamental reason you are reading the page. Element  
content will be rendered though, so you have to manually find out where it  
ended. Since screen reader users are ill-equipped to scan, this really  
means hearing it all the first time, and learning and remembering enough  
of the structure that is specific to this instance to skip reliably to the  
next bit. In particular, current user agents give you no safe way to avoid  
reading the whole lot the first time through.

By contrast, in a case where something conveys a lot but has very simple  
semantics *in context*, you can happily have a very short equivalent, with  
the ability to follow a longer one.

An alternative to longdesc is the SVG-style elements (in SVG they are  
called desc and title). They might be an option for elements with content.  
They are not an option of img, and I don't think we can realistically  
remove the element from HTML.

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 09:50:49 GMT

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