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Re: assistive tech and layout tables

From: <jukka.korpela@tieke.fi>
Date: Thu, 21 Feb 2002 09:53:15 +0200
To: w3c-wai-ig@w3.org
Message-ID: <OFAAC7CD9F.02615896-ONC2256B67.0027A6A7@tieke.fi>

Michael Fry wrote:

> I've been asked to determine if assistive technologies, e.g.
> screen readers, can be "directed" by HTML (or something else)
> to read specific cells in a layout table in a particular order

Your assumption that the answer is "no" sounds correct, since there
is no HTML markup or CSS properties for suggesting a reading order,
and any heuristic guesses would really be shots in the dark.
There might be some work in progress to add features into CSS for this,
but what comes closes in _current_ CSS (which is still poorly implemented
in browsers) in section "Audio rendering of tables" in CSS2:
http://www.w3.org/TR/REC-CSS2/tables.html#q21
and it deals with rendering of tables used for presenting tabular data,
not layout tables, and it's interested in the (very important) question
of association data cells with headers, to indicate the meanings of
data in cells.

Even if something related will be added into CSS, it will take quite
some to get it implemented. Besides, there would be the problem that
we now have with a somewhat analogous construct, the tabindex attribute:
authors who use it often _rely_ on it, causing problems to people using
programs that don't support the construct at all.

And, basically, layout tables are something we should try to get rid of,
replacing them with the use of CSS positioning and other CSS features
for suggesting layout. Authors who keep using layout tables might
consider using tricks like Delorie's trick of using a dummy cell to make
the order better when tables are processed rowwise, see
http://www.delorie.com/web/ses-hint.html
DJ Delorie presents that as a trick to make search engines "see" a
document's content in a certain order, but it would work for speech
synthesis, too, when performed rowwise by the table structure (and not
according to what has been written onto the screen)

> On a potentially related note, what do people think about providing
> *several* 'skip navigation' links on a page, e.g. one for 'main content,'
> one for 'main navigation,' 'local navigation,' etc.

It might help, if the page is confusingly complex. I'd say it could be
useful partial workaround if you don't want to _solve_ the problem. :-)
But if you ask me, I wouldn't intuitively know, for example, what
"local navigation" means. Local to what? (The page? The site? Some
geographic locality?)

> Is there a reason
> why are 'skip nav' links seem to be limited to one per page?

Not really, I think, but they are commonly presented as a workaround
needed to skip over _one_ bulk of irrelevant (for normal use) content.
That is, all the different sets of navigational links are regarded
as one bunch, to be skipped. If they contain, say, a table of content
for the current page, then that set of links is not skippable in the
same sense as "navbars" are. A table of content, which is of course
not normally an HTML table but a list, is what users normally start
with, so I'd make a "skip nav" link point to the start of the table
of content. If the user wishes to skip to the beginning of the
content proper, e.g. because he has already studied the table of
content during his previous visit to the page, he can conveniently
use the first item in the table of content. Assuming that the items
there are links to the corresponding parts of the text, of course,
as they should be.

All these "skip over" links are workarounds, not solutions. It is
symptomatic that we find it necessary to use _verbs_. Cool links are
nouns or noun phrases, not verbs, since they refer to something, instead
of telling to do this or that. (Actually, it isn't always necessary
to use verbs for "skip over" links; "main content" or something
like that might be better.)

For constructs like a <pre> block or other things that are potentially
very problematic in some modes of use and to some users, "skip over"
links are the practical solution at present, unless you can feasibly
put the problematic content itself behind a link, on a page of its own.
But it is then important to make clear _why_ the user might wish to
skip over something and what (if anything) will be missed that way
and, hopefully, where a more accessible presentation is available.

--
Jukka K. Korpela, erityisasiantuntija / senior adviser
TIEKE Tietoyhteiskunnan kehittämiskeskus ry
Finnish Information Society Development Centre
Salomonkatu 17 A, 10th floor, FIN-00100 HELSINKI, FINLAND
Phone: +358 9 4763 0397 Fax: +358 9 4763 0399
http://www.tieke.fi  jukka.korpela@tieke.fi
Received on Thursday, 21 February 2002 02:55:30 GMT

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