+++ This bug was initially created as a clone of Bug #18790 +++

Hi,

In the Editor's Draft 4 September 2012, "Section 4.9.6 The thead element" show a method about on how to add a description to a column header cell.

The "algorithm for assigning header cells" defined in the "Section 4.9.12.1 Forming a table" do not add any particular meaning to those describing cell because they are parsed with the "internal algorithm for scanning and assigning header cells", the same algorithm for parsing the real data cell. 

This can create a confusion between the real data cell vs. the describing cell in a table because the "internal algorithm for scanning and assigning header cells" are not considering any column group and/or any row group.

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Describing cell for a row header cell


I would like to propose an addition in the specification about on how to add a description to a row header cell in a data table. That relation can be made by using the colgroup element. 
See the draft of that technique:  http://wet-boew.github.com/wet-boew/docs/tableparser/rowheader-description-techniques.html (FYI, the intention of that technique is for submission to the WCAG 2.0 Techniques)

A note in the section "4.9.3 The colgroup element" can be added to say "the first column group (colgroup element) can be used as an header column group if inside the column group there are at least one row header cell defined inside a tbody row group. Otherwise the first column group would be a data column group." 

With that note, it would be possible to set a descriptive cell to a row header cell.

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Attached: A javascript table parser that takes in consideration the row group, the column group and the placement, size of the header cell to create the relationship between each cell contained in a table. You can find the most recent version here: https://github.com/wet-boew/wet-boew/blob/master/src/js/workers/parser.table.js

The following table validator use the preceding table parser.
http://wet-boew.github.com/wet-boew/docs/tableparser/validator-htmltable.html

FYI - Here a mailing sent to WAI Interrest Group about a request for comments in regards of the techniques mentioned here. http://lists.w3.org/Archives/Public/w3c-wai-ig/2012JulSep/0310.html

Thank you

:-)

Pierre Dubois