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Re: function and impacts (was: @scope and @headers reform)

From: Leif Halvard Silli <lhs@malform.no>
Date: Tue, 23 Sep 2008 18:40:39 +0200
Message-ID: <48D91C07.9000605@malform.no>
To: joshue.oconnor@cfit.ie
CC: Henri Sivonen <hsivonen@iki.fi>, James Craig <jcraig@apple.com>, Al Gilman <alfred.s.gilman@ieee.org>, Chris Wilson <Chris.Wilson@microsoft.com>, W3C WAI-XTECH <wai-xtech@w3.org>, public-html@w3.org, Gez Lemon <gez.lemon@gmail.com>

Joshue O Connor 2008-09-23 14.45:

> Henri Sivonen wrote:
>> For the use cases your clients have, would it be necessary to 
>> use/recommend headers/id if browsers implemented the Smart Headers 
>> algorithm Ben mentioned and reported those associations to AT?
> 
> I don't know yet. I am not sure that it is the right solution.


I have partly confused the "Smart headers algorithm" with the 
Experiemental algorithm in James Graham's Table Inspector. [1] The 
latter can interpret <td><strong> as a header cell. *That* aspect 
of the Experimental algorithm is similar the role of @axis in the 
HTML 4 algorithm: Both methods let's a TD cell play the role of a 
header cell. :-)

[1] http://james.html5.org/tables/table_inspector.html

However, the Smart Algorithm, which can be tested in the Table 
inspector as well, does not include whether <td><strong> nor @axis 
in its headers fact finding mission.

Section 11.4.2 of HTML 4 contains an Table with the axis 
attribute, that I have published. [2] I have also published a 
modified version of that table, where I deleted its @headers 
attributes, in order to test the pure effect of the @axis 
attributes when using the HTML 4 algorithm (which incorporates 
both @headers and @axis as part of the algorithm). [3]  Then I ran 
the that page in the Table Inspector. [4]

[2] http://www.malform.no/html5/axis-original
[3] http://www.malform.no/html5/axis+
[4] http://tinyurl.com/axis-effect

If you perform that test yourself [4] - please also try the other 
algorithms on offer, then you will see that a) for the HTML 4 
algorithm, @axis is taken into account, allowing you to include 
cells into the algorithm witout marking anything up as headers, b) 
it is only the HTML 4 algorithm which can do this. Both the Smart 
and the HTML 5 draft algorithm requires that you use TH cells to 
achieve the same thing.

(Using the @headers attribute to achieve the same thing, requires 
a lot of repetitive @headers attribute - whichever algorithm one 
choses. As can be seen in the original table.)

 
> For the record, if a new authoring method works (i.e is well, supported, 
> easy to author/understand etc) I have no problem recommending it. With 
> this issue I am very concerned with legacy use but I do concede that if 
> a solution is semantically superior at some stage a clear break must be 
> made in favour of it.
> 
> But this is not a black and white issue, there are many shades of grey. 
> For example, support by AT for @scope is practically non-existent. 
> Anecdotally, it seems to me that many tables that use @scope just happen 
> to coincide in their design to how the screen readers heuristic 
> evaluation understands the content pattern, rather than because @scope 
> had been used to mark up the content.
> 
> So I guess, it doesn't pay to think in terms of absolutes.


The algorithm of HTML 4 comes in 2 parts: A *primitive algorithm*, 
which only takes place when the start-point cell has the headers 
attribute. And a *full algorithm,* which takes place when it 
doesn't have the @headers attribute. (Both, however, are really 
the same algorithm.)

I suppose that AT support for the *full* HTML 4 algorithm is also 
not quite there? (Though, any AT software which incorporates the 
@axis cells in my HTML 4 based example (see [4] above) proves that 
they at least are close to support it.)

However, even if support for the full HTML 4 algorithm should not 
be any better than support for the HTML 4 scope attribute,  the 
question still is what would work best?

Either, getting AT software to extend their @headers support to 
support for the full HTML 4 algorithm (which incorporates the 
@headers attribute, when present)?

Or, to ask that AT software take care *never* implements anything 
*but* the primitive @headers algorithm and instead implement 
support for the @scope attribute.

The @headers-incorporating HTML 4 algorithm at least has one thing 
going for itself: It is much easier to grasp than the Smart 
Algorithm. (But that is not to say that the HTML 4 could not be 
smartened up.)

PS: I can only thank James for having made such a decent and 
honest Table Inspector!
-- 
leif halvard silli
Received on Tuesday, 23 September 2008 16:41:33 GMT

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