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Review UA Guidelines 5.4 Tables

From: Harvey Bingham <hbingham@acm.org>
Date: Wed, 24 Feb 1999 02:22:01 -0500
Message-Id: <199902240732.CAA11990@mail-out-3.tiac.net>
To: w3c-wai-ua@w3.org
5.4 Ensure that tables are accessible

[Rather than the first paragraph jumping into complex tables, I'd start with
the distinction layout table vs data tables.]

Tables are used to organize data, and in HTML have been used to layout
pages where the parts of the table are unrelated.

Data tables have distinct TH head cells and TD data cells. The TD cell
content gains gain implicit identification from TH cells in the same 
column and/or row.

Tables are also used to achieve limited control over two-dimensional layout
of information otherwise unrelated. For these layout tables, a user agent
can assist the reader by indicating that no relationship should be expected.
Use of TH cells just for their formatting purpose in layout tables is
discouraged, as those TH cells imply that some TD cells should gain meaning 
from the TH cell content.

5.4.2. Provide access to header information for a given cell.

Suggest that the user may choose the form and amount of this
information, possibly announcing the row heads only once and then
the column head or its abbreviation abbr="..." to announce the TD content.

5.4.3 [Priority 1] 
Allow the user to navigate among tables in a document. 

I question the need to navigate among tables, "table-tabbing". Most 
tables stand alone. I certainly doubt it is Priority 1. 

If an author feels it is important to link the tables, that author 
should provides a list of tables (LOT) with hyperlinks to the tables. 
If such is present, then the table order is deemed significant for the 
reader, and that list should suffice. I believe there is no need for a 
user agent to facilitate this. If the author is concerned, an 
<a href="..." rev="LOT">...</a> pointing back to the list of tables
should suffice.

5.4.4 Allow the user to navigate among table cells of a table (notably
left/right within a row and up/down within a column). 

Navigation must maintain cognizance of encountered cells with
implicit content resulting from spans.

That assumes that the table writing direction is left-to-right.
The natural language of the table may cause the table to have dir="rtl", 
right-to-left for order of the cells in a row (and order of letters in
a word, and words in a phrase.) Any row stub TH cells will by 
default be on the right, rather than on the left. The colspan horizontal 
spanning direction is leftward, so the right-most cell contains 
the content. That content is not repeated in cells to its left.

That can get further obscured if the writing directions change row-to-row,
say to allow boustrophedon writing (as the oxen plow)!

Regards/Harvey Bingham  
Received on Wednesday, 24 February 1999 02:32:05 UTC

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