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Re: WCAG 1.0 CP 6.1 Considered Harmful [was: Re: who does what]

From: Wendy A Chisholm <wendy@w3.org>
Date: Tue, 25 Sep 2001 13:12:01 -0400
Message-Id: <4.2.0.58.20010925130848.00c76880@localhost>
To: "Sean B. Palmer" <sean@mysterylights.com>, <w3c-wai-gl@w3.org>
Cc: "William Loughborough" <love26@gorge.net>
Yes, this is an issue in WCAG 1.0 which is why in WCAG 2.0 we very 
carefully say, "Checkpoint 4.4 Ensure that content remains usable when 
technologies that modify default user agent processing or behavior are 
turned off or not supported. "  This is also why in my explanation I only 
called out HTML since it does have a default rendering.

Issuing an erratum for 1.0 is a good idea.  Do you agree it can be based on 
the work we've done in 2.0?

--wendy

At 01:03 PM 9/25/01 , Sean B. Palmer wrote:
>[Summary: WCAG 1.0 CP 1.6 is IMO harmful, should be revoked in the errata
>for WCAG 1.0, and purged altogether from WCAG 2.0.]
>
>[...]
> > In our last discussion of the issue, we felt that the scenarios that
> > were being used to make the case fell under the requirement to
> > use style sheets with HTML in a way that when style sheets fail,
> > are not supported or turn off that the content is still readable.  For
> > example, a sidebar should fall into the flow of the content (likely
> > at the beginning or the end).
>
>So... the arguement has been made that classes do not need to have
>semantics attached to them because of checkpoint 6.1 in WCAG 1.0? Well, I
>think that exposes a *serious* flaw in that checkpoint.
>
>There is *no* default rendering for markup documents on the Web that are
>not in some way recognized by the UA. For example, if one feeds an XML
>document as-is into MSIE5+ or Ns6+, IE5 shows the outline of the document,
>and Ns just renders the text as if the markup weren't there. It is only
>when one attaches a stylesheet through use of the xml-stylesheet PI that
>any presentation is added to the document at all (via. CSS and or XSLT).
>
>When a browser recieves a document that is of text/html MIME type
>(according to what it can deduce from the HTTP headers), then it recognizes
>that the document should be rendered as text/html, and applies its
>knowledge base of HTML to the document for output. That includes behaviours
>for form controls etc., but most noticably it includes the presentational
>aspect of the document. In other words, there is a default stylesheet
>*built-into* the browser.
>
>Now, most browsers will not let one turn off the built-in stylesheet (I
>think Ns6+ lets one play with it), but that does not mean that it isn't
>there. A default UA presentation is still what WCAG considers to be a
>"stylesheet", and yet when it is turned off, a page will often not still be
>readable. So all pages are in violation of CP 6.1. That is not the fault of
>the Web pages of the world, it is a fault with CP 6.1, and that is the
>reason I believe CP 6.1 to be a checkpoint which should be revoked in the
>errata for WCAG 1.0, and purged altogether from WCAG 2.0.
>
>The semantics of HTML are well known because of HTML's pervasiveness. But
>one should not conclude that default (especially visual) renderings are
>inherent to HTML itself. If I want to override <p> displaying as a block
>level element, then I can quite easily do so:-
>
>    p { display: inline; }
>
>HTML has no *standard* "view". There are hints in the HTML 4.01
>soecification as to how it MAY be rendered, but these barely constitute a
>*default* rendering, yet alone a *standard* rendering. XHTML 2.0 will
>hopefully break totally clear of these idioms, and I don't expect any XHTML
>2.0 UA to have a built in stylesheet. It doesn't really need to have it.
>
>I think Nick Kew put it best in his recent www-validator rant:-
>
>[[[
>(1) The novice (or non-technical website owner) question:
>     "my site looks right and works fine - isn't that enough?"
>
>The answer to this one is that markup languages are no more than
>data formats.  So a website doesn't look like anything at all!
>]]] - http://lists.w3.org/Archives/Public/w3c-wai-gl/2001JulSep/1071
>
>So, this brings us back to the question of whether or not classes should
>have semantics associated with them. Since I have just discussed how CP 6.1
>is in ignorance of some pretty basic Web axioms, this checkpoint cannot be
>used as a fallback. Classes are (whether a good mechanism or not) a method
>of attaching additional semantics to elements in XHTML, and as such, the
>author MUST have a way to make those additional semantics known. Otherwise,
>classes are ambiguous, and therefore are not fully accessible.
>
>--
>Kindest Regards,
>Sean B. Palmer
>@prefix : <http://webns.net/roughterms/> .
>:Sean :hasHomepage <http://purl.org/net/sbp/> .

--
wendy a chisholm
world wide web consortium
web accessibility initiative
seattle, wa usa
/--
Received on Tuesday, 25 September 2001 13:10:10 GMT

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