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WCAG response on comments regarding WCAG conformance claims

From: Christophe Strobbe <christophe.strobbe@esat.kuleuven.be>
Date: Wed, 06 Jun 2007 11:03:07 +0200
Message-Id: <>
To: ERT WG <public-wai-ert@w3.org>


I thought you mgiht be interested in the following. Last year, we had 
a discussion on this list about WCAG conformance claims [1], which I 
summarized and forwarded to the WCAG WG list [2]. I also submitted a 
comment about this through the comment submission system (LC-1470).
Below is that comment and the response by the working group [3]:


The definition of Web unit is still ambiguous.

(1) If an HTML document (home.htm) has various linked stylesheets (one
for screen, one for print, one for projection, ...), these are not all
intended to be rendered together. I think the 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\',
- ...
However, this is not clear from the definition. If these are all
different web units, it is also impossible to identify them with a
URL, because the URL is the same for each.

(2) If an HTML page uses an object element with one or more fallbacks
nested inside it (see the example slightly below
I think the Web unit you claim conformance for is the HTML document
with the outermost object element (with the TheEarth.py applet).
However, the content of each of the nested object elements is not
meant to be rendered together with the content of all the other object
elements. Does that mean that there is a different web unit per
fallback/nested object element?

(3) If a web page uses frames, the content of some of the frames
depends on the user\'s interaction: e.g. clicking a link in the
navigation frame opens a different document in the content frame. So
the URL that identifies the frameset document does not always identify
the same Web unit, unless the Web unit is limited to what is loaded by

(4) If user agent X requests URL 
<http://www.example.com/>http://www.example.com/ with MIME
type aaa/bbb and user agent Y requests the same URL with MIME type
ccc/ddd, and they get different web units because of the different
MIME type, the URL cannot be used to differentiate between the two web
units. Does that mean these are different Web  units according to the
current definition?

Most of this was previously discussed on the ERT mailing list in the
context of conformance claims (see
and next messages in the same thread) and forwarded to the GL list

Proposed Change:

Response from Working Group:

We have revised the guidelines and eliminated the word "Web unit" in
favor of "Web page." We have defined "Web page"as follows (see

Web page

     a resource that is referenced by a URI and is not embedded in
another resource, plus any other resources that are used in the
rendering or intended to be rendered together with it

     Note: Although any "other resources" would be rendered together
with the primary resource, they would not necessarily be rendered
simultaneously with each other.

     Example 1: When you enter 
<http://shopping.example.com/>http://shopping.example.com/ in your
browser you enter a movie-like interactive shopping environment where
you visually move about a store dragging products off of the shelves
around you into a visual shopping cart in front of you. Clicking on a
product causes it to be demonstrated with a specification sheet
floating alongside.

     Example 2: A Web resource including all embedded images and media.

     Example 3: A Web mail program built using Asynchronous JavaScript
and XML (AJAX). The program lives entirely at 
but includes an inbox, a contacts area and a calendar. Links or
buttons are provided that cause the the inbox, contacts, or calendar
to display, but do not change the URL of the page as a whole.

     Example 4: A customizable portal site, where users can choose
content to display from a set of different content modules.

To answer your questions:

According to our definition.

#1 -   They are all the same Web page because they are all the same
primary resource with different secondary resources rendered with

#2 Again they are all the same Web page including all the nested
versions.   The secondary resources do not need to be rendered
simultaneously with each other, only with the primary, to be part of
the same Web page.

Regarding your concern #3, the definition of Web page is purposefully
written to include dynamic content that comes from the same URI.  So
all of the content from all the variations would be part of the web
page. If the contents of the frames can be loaded separately as well,
then they would also be separate Web pages as well. But they would
still be part of the frame Web page.

#4  If the different mime type would cause a different PRIMARY
resource to be loaded, then they would be different Web pages.   If
you included that URI in your claim, all Web pages from that URI would
have to be conform (meet the success criterion or have a mechanism to
obtain a page with the same content that did).


[1] <http://lists.w3.org/Archives/Public/public-wai-ert/2006May/0029.html>
[2] <http://lists.w3.org/Archives/Public/w3c-wai-gl/2006AprJun/0181.html>
[3] Comment 7 at 

Best regards,


Christophe Strobbe
K.U.Leuven - Dept. of Electrical Engineering - SCD
Research Group on Document Architectures
Kasteelpark Arenberg 10 bus 2442
B-3001 Leuven-Heverlee
tel: +32 16 32 85 51

Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm
Received on Wednesday, 6 June 2007 09:03:19 UTC

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