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Re: WCAG 2.0 Conformance Claims

From: Christophe Strobbe <christophe.strobbe@esat.kuleuven.be>
Date: Thu, 11 May 2006 22:53:27 +0200
Message-Id: <6.0.0.22.2.20060511221545.02af9980@mailserv.esat.kuleuven.be>
To: public-wai-ert@w3.org



Carlos Velasco asked
<blockquote>
what happens when a delivery unit (...) has a CSS like 
http://example.com/css/example.css? It is in scope or not?
</blockquote>


Christophe Strobbe responded:
<blockquote>
A stylesheet is not a Web unit but an "authored unit", and when it is 
"intended to be used as a part of another authored unit", it is an 
"authored component" 
(http://www.w3.org/TR/WCAG20/appendixA.html#authored-componentdef).
Conformance claims apply to Web units, not to authored units. So if a Web 
unit within the scope of your conformance claim uses a CSS that is outside 
the scope of your conformance claim, my understanding is that the 
conformance claim applies to the Web unit *with* the CSS (but not to the 
CSS in isolation).
</blockquote>


Then Johannes Koch wrote back:
<blockquote>
Let's make it a little more complicated :-) As Carlos Iglesias quoted, a 
Web Unit is

   "A collection of information, consisting of one or more resources,
   intended to be rendered together, and identified by a single Uniform
   Resource Identifier (such as URLs)".

Let's consider an HTML document with various linked stylesheets, one for 
screen, one for print, one for projection, ... They are not intended to be 
rendered (all) together. So which CSS file belongs to the Web Unit 
identified by the HTML document's URL? Or are there different Web Units for 
each CSS file together with the HTML document. But how do I identify them? 
The HTML document has only one URL.
</blockquote>


You can't make assumptions about how the type of user agent that will be 
used to render the HTML document: on a screen, through projection, on a 
refreshable braille display, with speech synthesis, ... So if the HTML 
document, say 'home.htm', has stylesheets for each of these media types, 
the following would all count as Web units:
- home.htm with the CSS for 'screen',
- home.htm with the CSS for 'projection',
- home.htm with the CSS for 'braille',
- home.htm with the CSS for 'aural',
- ...

So the question becomes: if you have a conformance claim that has the above 
'home.htm' in its scope, does the conformance claim cover each of the above 
examples? Since you can't make assumptions about the user agent, I think 
the answer is yes.
(How you represent this in EARL is another matter.) I don't think it makes 
sense to define the Web unit as home.htm + screen.css + projection.css + 
braille.css, ...


Come to think of it: if you use an object element with one or more 
fallbacks nested inside it (see the example slightly below 
http://www.w3.org/TR/1999/REC-html401-19991224/struct/objects.html#idx-object-5), 
I think the Web unit you claim conformance for is the HTML document with 
the outermost object element (with the TheEarth.py applet). Now let us look 
at a few scenarios.

1. Let us assume that Python applets are not in the baseline and that there 
is a fallback for each Python applet using a technology within the 
baseline, then the conformance claim applies to the fallback (and the 
Python applets must not interfere with the content). I don't know if EARL 
can take baselines into account (I'm too tired to check now). Maybe a 
"Baseline Description Language" would be useful?

2. Alternatively, let us assume that Python applets are in the baseline and 
there is a fallback for each Python applet using another technology within 
the baseline. What happens if the Python applet cannot be retrieved from 
the server, so that the fallback is used instead. How does this affect the 
conformance claim? Can EARL make statements about the HTML document + 
fallback object?

3. Let us assume that Python applets are in the baseline and there is a 
fallback for each Python applet using another technology outside the 
baseline. (I think this is not very logical, but it is possible.) What 
happens if the Python applet cannot be retrieved from the server, so that 
the fallback is used instead. How does this affect the conformance claim? 
(To be continued...)

Regards,

Christophe
-- 

Christophe Strobbe
K.U.Leuven - Departement of Electrical Engineering - Research Group on 
Document Architectures
Kasteelpark Arenberg 10 - 3001 Leuven-Heverlee - BELGIUM
tel: +32 16 32 85 51
http://www.docarch.be/ 


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Received on Thursday, 11 May 2006 20:53:39 GMT

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