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RE: BIG ISSUE -- re Delivery Units

From: Gregg Vanderheiden <gv@trace.wisc.edu>
Date: Fri, 10 Feb 2006 12:59:15 -0600
To: "'Carlos A Velasco'" <Carlos.Velasco@fit.fraunhofer.de>
Cc: <w3c-wai-gl@w3.org>
Message-ID: <00ee01c62e74$16a31b70$ee8cfea9@NC6000BAK>

Hi Carlos,

Images as delivery units cannot meet the guidelines because there is no
place in a jpg file to put an alt text.

An HTML page with images in it can conform.  But the image itself cannot.
And the image itself is a delivery unit. 

That is why we are introducing Web Unit.   There is no DI equivalent term.  

Gregg

 -- ------------------------------ 
Gregg C Vanderheiden Ph.D. 
Professor - Ind. Engr. & BioMed Engr.
Director - Trace R & D Center 
University of Wisconsin-Madison 
The Player for my DSS sound file is at http://tinyurl.com/dho6b 

-----Original Message-----
From: w3c-wai-gl-request@w3.org [mailto:w3c-wai-gl-request@w3.org] On Behalf
Of Carlos A Velasco
Sent: Friday, February 10, 2006 7:32 AM
To: Gregg Vanderheiden
Cc: w3c-wai-gl@w3.org
Subject: Re: BIG ISSUE -- re Delivery Units


Hi Gregg,

As a first remark, IMHO this WG shall run away from reinventing the wheel. I
think that <http://www.w3.org/TR/di-gloss/> and the HTTP specification shall
cover the needs of WCAG. If something is not clear from the DI stuff, then
let us ask them, as Johannes did in the past. 
That said ...

Gregg Vanderheiden wrote:
> Johannes wrote:
>> Don't you define the "Web Unit" to be exactly this [Delivery unit]?
> 
> See the problem statement (below)
> 
> Each image is a DU
> Images can't meet the Guidelines on their own.

Why should they? They are images with no alternative text or description.
Also I am sure you are aware that you can include metadata in several media
formats (although I am not so sure whether they have a field for
descriptions, nor that UAs can read them).

> Hence, as written - the guidelines cannot be met by any site or page 
> that has an image on it.

Sorry, but that line of inference is not true. Guidelines are not met by
"sites", they are met by sets of resources (or DUs, or whatever you end up
calling them) that you must specify in any conformance claim. 
Otherwise, you may have to think/reuse a definition of "site" (or "hosts" or
"domains") to apply WCAG 2.0 to them.

regards,
carlos

--
Dr Carlos A Velasco - http://access.fit.fraunhofer.de/ Fraunhofer-Institut
für Angewandte Informationstechnik FIT
   [Fraunhofer Institute for Applied Information Technology (FIT)]
   Barrierefreie Informations- und Kommunikationstechnologie für Alle
   Schloss Birlinghoven, D53757 Sankt Augustin (Germany)
   Tel: +49-2241-142609 Fax: +49-2241-1442609
Received on Friday, 10 February 2006 18:59:19 GMT

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