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From: Gregg Vanderheiden <po@trace.wisc.edu>
Date: Thu, 2 Jul 1998 19:57:24 -0500
To: "'GL - WAI Guidelines WG'" <w3c-wai-gl@w3.org>
Message-ID: <002201bda61d$8b597500$LocalHost@vanderheiden>
In our conf call we came to the tentative conclusion that we
should only require additional semantic tagging of tables if they
exceeded the algorithm listed in the HTML 4.0 spec.

Daniel posted an earlier memo on this which can be seen at

The actual algorithm (taken directly from the HTML 4.0 spec at
11.4.3 Algorithm to find heading information
In the absence of header information from either the scope or
headers attribute, user agents may construct header information
according to the following algorithm. The goal of the algorithm
is to find an ordered list of headers. (In the following
description of the algorithm the table directionality is assumed
to be left-to-right.)
* First, search left from the cell's position to find row header
cells. Then search upwards to find column header cells. The
search in a given direction stops when the edge of the table is
reached or when a data cell is found after a header cell.
* Row headers are inserted into the list in the order they appear
in the table. For left-to-right tables, headers are inserted from
left to right.
* Column headers are inserted after row headers, in the order
they appear in the table, from top to bottom.
* If a header cell has the headers attribute set, then the
headers referenced by this attribute are inserted into the list
and the search stops for the current direction.
* TD cells that set the axis attribute are also treated as header



-- ------------------------------
Gregg C Vanderheiden Ph.D.
Professor - Human Factors
Dept of Ind. Engr. - U of Wis.
Director - Trace R & D Center
GV@tracecenter.org , http://tracecenter.org/
FAX 608/262-8848
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Received on Thursday, 2 July 1998 20:58:56 UTC

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