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Re: Proposal to address issue of scope of guideline 11

From: Charles McCathieNevile <charles@w3.org>
Date: Mon, 14 Jun 1999 20:17:20 -0400 (EDT)
To: Jason White <jasonw@ariel.ucs.unimelb.edu.au>
cc: Web Content Accessibility Guidelines <w3c-wai-gl@w3.org>
Message-ID: <Pine.LNX.4.10.9906142007220.14809-100000@tux.w3.org>
The use of CSS is possible for HTML and for XML. But there are other
approaches to solving the problem. For example in an HTML 3.2 world without
CSS (which unfortunately is where many people still think they are living) it
is perfectly possible to properly control the colours of certain document
elemnts, secure in the knowledge that this can be easily over-ridden. On the
other hand, the only mechanism available for controlling positioning - the
abuse of tables, is not very easily over-ridden - it only comes with access
to the DOM (or brutal reinterpretation of the source).

Likewise, PDF does not allow control of the presentation. Which is why it is
not accessible, and therefore should not be used for web content.

Certainly the best approach is to use style sheets, along with other w3c
standards. I think there is a case for saying, in paralell with the until
user agents... clauses, "when user agents provide support for X, stop doing
Y.

The way that priorities are defined, we have to show that there is an
(effectively) impassable barrier to make something a P1, or a significant
barrier to make something P2. Things that are good ideas become P3 - new
design should definitely take them into account, but they do not create
barriers by themselves.

Charles McCN



On Tue, 15 Jun 1999, Jason White wrote:

  On Sun, 13 Jun 1999, Charles McCathieNevile wrote:
  
  > 
  > Using style sheets is an HTML-specific techique for "Use methods which can
  > be over-ridden by the user to control presentation".
  
  Style sheets are definitely not HTML specific: both CSS and XSL are
  intended to apply to XML documents as well. Indeed, having an appropriate
  medium-specific style sheet for one's output device is even more important
  in the case of XML document types, where no reasonable default rendering
  can be supplied by the user agent.
  
  Regarding the importance of using the latest W3C specifications, I can
  think of several cases where there are specific access advantages,
  including: (1) HTML 4.0 compared with earlier versions; (2) CSS 2
  positioning; (3) MathML as opposed to the use of images; (4) Smil as
  opposed to other multimedia formats that do not include access features.
  The access benefits of HTML 4.0 and CSS 2 are described in detail in
  relevant WAI publications, and there are similar advantages to be gained
  from the other formats mentioned. I think these benefits are so
  significant that checkpoint 11.1 deserves its priority 2 rating.
  
  In relation to PDF, one might be able to achieve Level A conformance in
  some circumstances using existing conversion technologies, provided that
  there are no multimedia objects in the PDF file and that the conversion
  software correctly determines the reading order of the document. However,
  PDF versions 1.2 and earlier do not support any genuine separation of
  content from presentation, and the conversion process is thus necessarily
  limited. PDF 1.3, with its support for a true structural tree, will
  resolve these drawbacks once it has been implemented by both authoring
  tools and conversion software.
  
  For the present, I fully support the existing checkpoint: properly
  structured HTML documents must be provided alongside any proprietary
  document formats that are to be used.
  
  

--Charles McCathieNevile            mailto:charles@w3.org
phone: +1 617 258 0992   http://www.w3.org/People/Charles
W3C Web Accessibility Initiative    http://www.w3.org/WAI
MIT/LCS  -  545 Technology sq., Cambridge MA, 02139,  USA
Received on Monday, 14 June 1999 20:17:30 GMT

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