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Colspans, rowspans, table accessibility

P: n/a
I've had this in the back of my head for a while. Take a look at
Example 1 on

http://gavelcade.com/table.html

There are three levels of column headings. All table accessibility
discussions I've seen would lead to the conclusion that you need to
use id and headers attributes on the headers and data cells,
respectively, for assistive technology to be able to correctly
associate data with headers.

But as long as I have THs on all the headers, does, or should,
assistive technology be able to figure out multiple levels of headers,
as long as the headers are in the same column or row as the data,
*taking rowspans and colspans into account*? It would make life so
much easier! The table in Example 1 would need no special markup at
all, beyond the td/th distinction.

Example 2 is for another question.
--
Harlan Messinger
Remove the first dot from my e-mail address.
Veuillez ôter le premier point de mon adresse de courriel.
Jul 20 '05 #1
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P: n/a
Harlan Messinger <hm*******************@comcast.net> wrote in message news:<ac********************************@4ax.com>. ..
I've had this in the back of my head for a while. Take a look at
Example 1 on

http://gavelcade.com/table.html

There are three levels of column headings. All table accessibility
discussions I've seen would lead to the conclusion that you need to
use id and headers attributes on the headers and data cells,
respectively, for assistive technology to be able to correctly
associate data with headers.

But as long as I have THs on all the headers, does, or should,
assistive technology be able to figure out multiple levels of headers,
as long as the headers are in the same column or row as the data,
*taking rowspans and colspans into account*? It would make life so
much easier! The table in Example 1 would need no special markup at
all, beyond the td/th distinction.


This might interest you, it goes into gory detail on that exact question:
http://www.ferg.org/section508/accessible_tables.html

--
Karl Smith.
Jul 20 '05 #2

P: n/a
Harlan Messinger wrote:
I've had this in the back of my head for a while. Take a look at
Example 1 on

http://gavelcade.com/table.html

There are three levels of column headings. All table accessibility
discussions I've seen would lead to the conclusion that you need to
use id and headers attributes on the headers and data cells,
respectively, for assistive technology to be able to correctly
associate data with headers.

But as long as I have THs on all the headers, does, or should,
assistive technology be able to figure out multiple levels of headers,
as long as the headers are in the same column or row as the data,
*taking rowspans and colspans into account*? It would make life so
much easier! The table in Example 1 would need no special markup at
all, beyond the td/th distinction.

[snip]

Karl's reference looks very comprehensive. But here is the W3C statement:
http://www.w3.org/TR/html401/struct/tables.html#h-11.4

--
Barry Pearson
http://www.Barry.Pearson.name/photography/
http://www.BirdsAndAnimals.info/
http://www.ChildSupportAnalysis.co.uk/
Jul 20 '05 #3

P: n/a
go************@kjsmith.com (Karl Smith) wrote:
Harlan Messinger <hm*******************@comcast.net> wrote in message news:<ac********************************@4ax.com>. ..
I've had this in the back of my head for a while. Take a look at
Example 1 on

http://gavelcade.com/table.html

There are three levels of column headings. All table accessibility
discussions I've seen would lead to the conclusion that you need to
use id and headers attributes on the headers and data cells,
respectively, for assistive technology to be able to correctly
associate data with headers.

But as long as I have THs on all the headers, does, or should,
assistive technology be able to figure out multiple levels of headers,
as long as the headers are in the same column or row as the data,
*taking rowspans and colspans into account*? It would make life so
much easier! The table in Example 1 would need no special markup at
all, beyond the td/th distinction.


This might interest you, it goes into gory detail on that exact question:
http://www.ferg.org/section508/accessible_tables.html


Section 11.4.1 in the HTML spec is so detailed, I guess I never looked
at 11.4.3, to which your reference directed my attention. If Ferg's
interpretation is correct, then table accessibility is *way* easier
than I've been treating it. In almost any case imaginable, for a given
data cell, the UA should be able to find the lowest-level row and
column header that goes with it, since it will virtually always be in
the same row or column as the data cell, and therefore one only has
mark up the header cells themselves with id and headers attributes.

But nowhere does Ferg justify his understanding that you can treat
rowspanned and colspanned header cells as "belonging", for this
purpose, to each of the columns or rows that they span visually. I'm
uncertain because if you could, I would have expected the W3C to have
*mentioned* it somewhere! That's what bugs me. Ack.

I guess I can try to find out what several aural browsers *do* do, and
go with that.

--
Harlan Messinger
Remove the first dot from my e-mail address.
Veuillez ôter le premier point de mon adresse de courriel.
Jul 20 '05 #4

P: n/a
Harlan Messinger <hm*******************@comcast.net> wrote:

The real-life state of affairs is just awful. I created the expanded
set of examples at http://gavelcade.com/table2.html, and tested it
with JAWS and IBM Home Page Reader. The results are discouraging
because the leave the sense that with current variations in the
technologies, I'm afraid that the best you can do might be either (a)
provide table accessibility formally, according to recommendations or
guidelines or regulations, ignoring what existing UAs do with it, or
(b) choose one UA to target, and hope other UAs do the same thing.

On the test page, ignore example 2. Examples 1 and 3 are as before.
Example 1 has no accessibility attributes, and Example 3 is identical
except for the "Country" header in the upper left-hand cell, which is
marked with scope="col".

Example 4 has id attributes in the column headings, and headers
attributes in the non-top-level column headings. It follows Ferg's
assumption that data cells will be associated with a TH found above
them or to the left of them, and that the TH's headers attributes will
then be followed to further associate the data cell with higher-level
headers.

Example 5 has both headers and data cells fully marked up with id and
headers attributes. Each data cell's headers attribute associates it
directly to all three levels of column headings, as well as to the row
heading. This could be redundant--data cells are associated with their
higher-level column headers both directly AND vis the lower-level
column headers to which they are associated.

Example 6 is like Example 5 except that the headers attributes in the
header cells themselves are removed, eliminating the redundancy noted
for Example 5.

Example 7 explicitly associates data cells only to the row header and
the lowest-level column header, rather than assuming that the UA will
figure out the lowest-level header as Example 4 did, but, like Example
4, leaves it to headers attributes within the header cells to provide
further associations to higher-level column headers.

The results listed below show what headers are spoken for (1) reading
a cell's contents; (2) changing row; (3) changing column. I refer to
"country" to indicate that the row header is read, and level1, level2,
and level3 for the three levels of column header. In every case, when
a header *has* been read, it has been the correct one for the cell.

Note that for HPR, Example 1, with no special markup at all, is
handled the best! The only less-than-optimal aspect of its handling of
Example 1 is that it reads all the column headers when the column is
changed, instead of just the headers that have changed.

JAWS

Example 1:
Read cell: level1 country
Change row: country
Change column: level1, whether it has changed or not

Example 3: same as Example 1

Example 4: same as Example 1

Example 5:
Read cell: level3 country level1 level2
Change row: country level1 level2
Change column: level3

Example 6: same as Example 5

Example 7:
Read cell: level3 country
Change row: country
Change column: level3

HPR

Example 1
Read cell: country level1 level2 level3
Change row: country
Change column: level1 level2 level3

Example 3: no headings read under any circumstances

Example 4: no headings read under any circumstances

Example 5:
Read cell: level1 level2 level3 country
Change row: level1 level2 level3 country
Change column: level1 level2 level3

Example 6:
Read cell: country level1 level2 level3
Change row: country level1 level2 level3
Change column: country level1 level2 level3

Example 7:
Read cell: country level3
Change row: country level3
Change column: country level3
--
Harlan Messinger
Remove the first dot from my e-mail address.
Veuillez ôter le premier point de mon adresse de courriel.
Jul 20 '05 #5

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