HTML5: Table headers attribute should only reference a TH with id?

I see that HTML5 headers  attribute requires that the cells referenced  in it point to TH with id and not TD with id.
I find this  strange and it sort of completely defeats the headers-id technique.
The technique is meant to address really complex tables that  are irregular and complex  often for reasons beyond the author's control.
So plain TH and scope are unlikely to make the table accessible.
Here the headers-id method gives the power to associate  a cell that is marked up as TD and visually serves as a header cell as a header for benefit of non-sighted users.
Is it really necessary to  put this constraint into the HTML5 standards?

See the Travel Expense Summary table in HTML 4.01 and the note in section11.4.2 that recognizes that  it is not always possible to mark  up a header cell as TH.
Sure for some complex tables where it is possible to mark up all header cells as TH and assign it an id-value,  the rule has little impact because the author can certainly mark them up as TH.
But where the author is constrained and cannot mark up a cell as TH and yet treat it as a header for other data cells, he will be at a loss. 
Maybe  one can flag a soft validation error so that if authors have accidently omitted to mark up a cell as TH it will be brought to their notice.
But it should not come in the way of accessibility.
Today NVDA depends on Firefox to expose the DOM and  table headers and Firefox does not expose a TD with an id as a header even if the headers attribute for a data cell refers to it. 
So please remove this constraint from the HTML specs.
Please see and support
Bug 881048 -Recognizing column headers marked up as TH in a table- improvement needed) – NVDA Community#3245(
https://bugzilla.mozilla.org/show_bug.cgi?id=881048

Sailesh Panchang
www.deque.com

Received on Friday, 21 June 2013 14:11:17 UTC