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Re: Tables - Gregg's email

From: Charles McCathieNevile <charlesn@sunrise.srl.rmit.edu.au>
Date: Sun, 5 Jul 1998 13:55:33 +1000 (EST)
To: Gregg Vanderheiden <po@trace.wisc.edu>
cc: "'GL - WAI Guidelines WG'" <w3c-wai-gl@w3.org>
Message-ID: <Pine.SUN.3.91.980705134506.28666E-100000@sunrise.srl.rmit.edu.au>
My first thought is that this is much too complex to include in the
guidelines. My second is that the goal of the guidelines is to teach good 
practise. So I am thinking along the following lines:

Guideline:
Modality independence, or Metadata requirements. Tables should include 
sufficient information to ensure that they can be accurately linearised 
(broken into plain text segments, for example) without any loss of 
information about what each piece of data is, or to what it is related.

Technique:
Use TH to provide headers for Table columns and rows.

Technique:
Where tables have structural divisions within them, which are not denoted 
by the structure of the table, nor by the row/column headers, use the 
additional table features of HTML 4.0 (SCOPE, AXIS, COLGROUP) to group the 
different structures.

Rationale:
UA's can only infer the structure of a table if it contains header and 
grouping information.

Reference notes:
What Gregg said. (included below)

Charles McCathieNevile

On Thu, 2 Jul 1998, Gregg Vanderheiden wrote:

> 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
> http://lists.w3.org/Archives/Public/w3c-wai-gl/1998JanMar/0213.ht
> ml
> 
> The actual algorithm (taken directly from the HTML 4.0 spec at
> http://www.w3.org/TR/REC-html40/struct/tables.html#h-11.4.3
> is:
> 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
> cells.
> 
> 
> Thoughts?
> 
> Gregg
> 
> 
> -- ------------------------------
> 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
> For a list of our listserves send "lists" to
> listproc@tracecenter.org
> 
> 
> 
Received on Sunday, 5 July 1998 00:17:36 GMT

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