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Re: Proposed change to checkpoint 5.3

From: Charles McCathieNevile <charles@w3.org>
Date: Fri, 16 Apr 1999 13:04:51 -0400 (EDT)
To: Chuck Letourneau <cpl@starlingweb.com>
cc: Jason White <jasonw@ariel.ucs.unimelb.edu.au>, WAI Markup Guidelines <w3c-wai-gl@w3.org>
Message-ID: <Pine.LNX.4.10.9904161248390.16032-100000@tux.w3.org>
I think that somewhere between the two lies the answer we seek.

A further proposal...

x.1
Tables must not be used for layout unless an appropriate reading order
is preserved when table is linearized. See also checkpoints 3.2,
3.3 and 3.4. [Priority 1]

techniques: Use style languages to associate presentation effects with
particular media-dependent renderings.

x.2
In tables used for layout, correct markup should be used to convey the
structure of the document (including headings, paragraphs, lists, etc.)
[Priority 2]

techniques: further discussion of how to do this 

x.3
Do not use structural markup to create presentation effects [Priority 3] 
 This makes it very difficult to interpret the structure of a document. In
 certain cases it can create significant problems - see (the checkpoints
 which deal with special cases)

techniques: Do not use TH, THEAD, etc in layout tables. Use Style
languages. A philosophical discussion of the need to design well so
accessibility can keep pace with general innovation. etc.

General notes:
This differs from Jason's proposal in that it requires tables which can be
linearised as priority 1 and effectively reduces the priority of using TH
etc to p3. It also provides a general principle of seperating style from
structure at a p3 level, with certain specific practices being p1 or p2
requirements.

It is possible to create fairly complex layouts without tables, which use
style sheets in a manner which transforms gracefully. We should dig out
the most complex such arrangements that we can find (I happen to have a
handy example - grin) and use them in the techniques to show how it is
done.

Charles McCN


On Fri, 16 Apr 1999, Chuck Letourneau wrote:

  While a few people have expressed some support for my proposed rewording of
  5.3 (and I thank you), I think that Jason's most recent attempt (5.3 and
  5.4 below) is very good and pretty succinctly captures his previous
  comments.  This wording gives us (authors) the flexibility we need to work
  with the current crop of agents and yet leads us not into temptation
  (pardon the ever expanding and probably irreligious religious theme I
  started.) <Grin>
  
  Cheers!
  Chuck
  
  At 16/04/99 12:12 AM , Jason White wrote:
  >
  >A formulation similar to the following might be appropriate (comments are
  >welcome):
  >
  >"5.3: Avoid using tables for layout unless the required formatting effects
  >can not be achieved with style language features supported by user agents.
  >(Priority 2).
  >
  >[Note discussing the evolution of style sheet positioning and the
  >anticipated implementation of this capability by user agents, and pointing
  >out that layout tables constitute an abuse of HTML markup as defined in
  >W3C Recommendations on HTML.]
  >
  >5.4 If tables are used for layout, (a) do not use TH cells to produce
  >special font effects; this will also enable screen readers, braille or
  >speech-based browsers, etc., to distinguish layout tables from those which
  >contain genuine tabular information. (b) Ensure that within the table
  >cells, correct markup is used to convey the structure of the document
  >(including headings, paragraphs, lists, etc.), and that an appropriate
  >reading order would be preserved if the table were linearized. See also
  >checkpoints 3.2, 3.3 and 3.4.
  >
  >Priority 2
  >
  >Note: Some screen readers can not decolumnize tables. It is therefore
  >necessary to avoid the use of layout tables, or provide an alternative
  >page, if a multi-column format is desired. See checkpoint 10.3."
  >
  >In the glossary, definition of linearization as applied to tables:
  >ignoring table-related markup, etc.
  >
  >
  
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--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 Friday, 16 April 1999 13:05:01 GMT

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