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Re: @headers on th too or just td?

From: Robert J Burns <rob@robburns.com>
Date: Fri, 27 Jun 2008 18:10:33 +0300
Cc: Dan Connolly <connolly@w3.org>, "public-html@w3.org WG" <public-html@w3.org>, public-comments-wcag20@w3.org
Message-Id: <3E0DBAE3-149A-4F7E-B65E-4B7B56A5C820@robburns.com>
To: Robert J Burns <rob@robburns.com>

Correction and clarification:

On Jun 26, 2008, at 10:56 PM, Robert J Burns wrote:

> HI Dan,
> On Jun 26, 2008, at 9:49 PM, Dan Connolly wrote:
>> I did a little investigation into ISSUE-20 table headers...
>> http://www.w3.org/html/wg/tracker/issues/20
>> attached are a couple files I was trying to make
>> into test cases.
>> The first one is from relevant WCAG 2 technique that somebody
>> referred me to...
>> H43: Using id and headers attributes to associate data cells with  
>> header
>> cells in data tables from Techniques for WCAG 2.0
>> http://www.w3.org/TR/WCAG20-TECHS/H43.html
>> I played around with that and validator.nu which led
>> me to discover that the current HTML 5 draft allows
>> @headers on td but not on th.
>> "The td element may have a headers content attribute specified."
>> -- http://www.w3.org/html/wg/html5/#the-td
>> Editor's Draft 25 June 2008
>> I suppose that suffices as far as I know... I can't
>> see any particular reason to use @headers on th, though
>> this does suggest the example in the WCAG 2 techniques
>> should get revised.
> For authoring simplicity headers on TH cells is more important than  
> headers on TD cells. In fact it would be better for document  
> conformance to allow them only on TH cells than to allow them on TD  
> cells. A properly specified data / header cell association algorithm  
> will already associate data cells with the most immediate header  
> cells. Allowing authors to associate those header cells with other  
> header cells means that authors only add the IDREF to a few header  
> cell rather than maybe thousands of data cells.
> I'm not aware if Ben came up within tables that needed headers on  
> the TD cells, but I can't come up with any off of the top of my head  
> (as long as @headers can be used on TH cells). However, not allowing  
> @headers on TD cells means authors have to repeat the same attribute  
> value thousands of times in some tables (where it would otherwise be  
> once or twice).
> Take care
> Rob

In the last sentence I miswrote. It should say:

"However, not allowing @headers on _TH_ cells means authors have to  
repeat the same attribute value thousands of times in some tables  
(where it would otherwise be once or twice)."

Removing the @headers attribute from TH cells creates a hardship for  
authors. However, @headers on TD cells is necessary for legacy AT  
which seldom implements the HTML 4.01 basic cell association algorithm  
(but hopefully will implement the HTML5 cel association algorithm  
whatever that ends up being).

So to sum up:

* We need headers attribute on TH cells
 We need headers attribute on TD cells, but only for legacy AT  
 We need to rethink the scope attribute which is confusing for authors
 We need to get UAs to implement cell association algorithms (one of  
the issues I wanted to raise was about this, but we WG members are no  
longer allowed to raise issues for issue tracking)

Take care,
Received on Friday, 27 June 2008 15:11:19 UTC

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