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RE: Is this complex table properly coded?

From: Jukka Korpela <jukka.korpela@tieke.fi>
Date: Tue, 3 Dec 2002 10:10:06 +0200
Message-ID: <621574AE86FAD3118D1D0000E22138A95BDF7A@TIEKE1>
To: "WAI (w3c-wai-ig@w3.org)" <w3c-wai-ig@w3.org>

RUST Randal wrote:

> Typically I avoid complex tables. 

Me too. But sometimes we cannot; sometimes a fairly complex
table is the most feasible way to present complex technical

> However, I need to add markup rules for complex tables into 
> my style guide.

I'm still struggling with the question what to recommend for
tables in general in my practical short guide to Web accessibility.
Considering the fact that most (data) tables on the Web make
little or no attempt at using any accessibility features,
even the distinction between <th> and <td>, I think I'll first
present the very basics of proper table markup, then proceed
to any extra markup we might add for accessibility. One reason
to this is that accessibility features for tables are the
most confusing thing in HTML markup related to accessibility.
When experts are confused, I can't really expect novices to
learn to use the complicated constructs easily; and using them
_wrong_ way is probably worse than not using them at all.

> I'm not sure that I'm using my ID and HEADER[S] attributes
> correctly.

As far I can see, your usage is correct: you use ID for
the TH elements and list (as a space-separated list) in a
HEADERS attribute in a TD element all the heading cells
(TH elements) that apply to the current cell.

However, the example is not very good in the sense that there
is little reason to use two levels of header cells. In fact
you will probably have difficulties in finding a real example
of such a situation where that would be needed and where
consequently you would need to use ID and HEADERS instead
of the much simpler approach of just using SCOPE attributes
in TH cells. In this example, it would be in several ways
better to have just the headers Title, Director, Star, and Co-Star.

I would also recommend using SCOPE in any case. There might
be user agents that recognize SCOPE but not HEADERS and ID.
Besides, SCOPE is a logical thing to use. Without it, TH
markup does not really tell whether the cell is a header
for a column or for a row (though heuristics might answer
this in most cases).

As regards to other issues in the markup (I'm interpreting the
question in the Subject line as a broad one):

> <table border="1" cellpadding="2" cellspacing="0" rules="rows"
> summary="Popular movies, the director, star and co-star." 

I would use a summary attribute that more clearly expresses
the content and structure of the table, e.g. "Information
about movies: Each row contains the title, the name of the
director, the name of the star, and the name of the co-star,
of a movie." Maybe this is just fine tuning.

> width="100%">

This, especially when combined with the width attributes for
the cells, reduces flexibility. This is a general design
issue rather than accessibility, but I cannot help noticing
that even in fullscreen mode, my IE shows the name "Harrison
Ford" as divided into two lines in the last column, when I
test your example. And such splits may have some impact
on accessibility. For a less known name, or for a hypothetical
reader who does not know Harrison Ford, the question may
arise in the reader's mind whether the cell tells about
two co-stars by their surnames or about a single co-star.

> 		<tr>
> 			<td headers="title">Star Wars</td> 

It might be argued that in a table like this, the cells in
the first row (movie titles) are logically headers for rows.
I would use <th scope="row" ...> here.

This is somewhat debatable of course, especially since
typical browsers display <th> elements by default centered
and in bold, and this might be undesired, even distracting.
The centering can be prevented using an explicit align="left".
Bolding is a different issue, but in practice, using CSS
(font-weight: normal) would probably be sufficient.

Jukka Korpela, senior adviser 
TIEKE Finnish Information Society Development Centre
http://www.tieke.fi/  My phone +358 9 4763 0397
Received on Tuesday, 3 December 2002 03:10:38 UTC

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