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Re: [html-techs] Table Type

From: Carlos A Velasco <Carlos.Velasco@fit.fraunhofer.de>
Date: Tue, 10 Feb 2004 17:27:37 +0100
Message-ID: <40290679.10507@fit.fraunhofer.de>
To: Chris Ridpath <chris.ridpath@utoronto.ca>
Cc: WAI WCAG List <w3c-wai-gl@w3.org>

Dear Chris, all,

My 2 cents of ¤.

On 02/10/2004 03:56 PM, Chris Ridpath wrote:
> Action from last weeks call to review issue 248[1] and compare to current
> draft document.
> 
> How to determine if a table is data or layout:
> 
> Discussed at length on this mailing list[2][3][4] etc.
> In summary - If cells can be moved without affecting their intrinsic meaning
> then it's a layout table. Corollary - If moving a cell affects its intrinsic
> meaning then it's a data table.

I think the definition is not more clear than before. This thing is one of those 
  for which everybody has some kind of mental representation, but you cannot 
nail a definition. Adding intrinsic to the word "meaning" is a subjective issue. 
What if the designer says that when you linearize her design, we are loosing its 
intrinsic meaning. The Free On-line Dictionary of Computing 
<http://www.foldoc.org>, defines table as "a set of data arranged in rows and 
columns". What is data: "Numbers, characters, images, or other method of 
recording, in a form which can be assessed by a human or (especially) input into 
a computer, stored and processed there, or transmitted on some digital channel." 
(from the same source). Back to square one:

I think the only resource with a better definition (not perfect either), is this 
one, already mentioned by Wendy:
<http://www.ferg.org/section508/accessible_tables.html#contents_item_3>

<quote>
We define a table as a presentation format for a set of data items and their 
associated metadata such that:

    1. Each data item is stored in a data cell
    2. The data cells are arranged in a two-dimensional grid called the table body
    3. The table has a title that indicates the nature of the data being presented
</quote>
Point 3 implies that the table must have a caption.

> Do not use structural markup for layout tables. Data tables must use TH
> elements. Layout tables can not use TH elements.[4][5]
> 

Sorry, but this is not true, according to the HTML spec:
<http://www.w3.org/TR/html4/struct/tables.html#edef-TD>

data cells (TD) can also be headers. Very clearly says:
"<!-- TH is for headers, TD for data, but for cells acting as both use TD -->"
That is what attributes @headers and @scope were created for.

The algorithm to identify headers is more complicated than the one depicted by 
Ben (look only for TH), but still doable. It is always good to look in the spec 
when issuing techniques.

regards,
carlos
-- 
Dr Carlos A Velasco - mailto:Carlos.Velasco@fit.fraunhofer.de
Fraunhofer-Institut für Angewandte Informationstechnik FIT
   [Fraunhofer Institute for Applied Information Technology (FIT)]
   http://access.fit.fraunhofer.de/
   Barrierefreie Informations- und Kommunikationstechnologie für Alle
   Schloss Birlinghoven, D53757 Sankt Augustin (Germany)
   Tel: +49-2241-142609 Fax: +49-2241-1442609
Received on Tuesday, 10 February 2004 11:28:27 UTC

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