Re: Draft text for summary attribute definition

Hi Gez,

On Feb 28, 2009, at 8:45 PM, Gez Lemon wrote:

> 2009/3/1 Robert J Burns <rob@robburns.com>:
>>> WCAG 2.0 does not recommend using summary="" for layout tables.  
>>> There
>>> is a note in one of the WCAG 2.0 techniques that states that a null
>>> summary is acceptable on layout tables [1], but it is not a WCAG 2.0
>>> recommendation.
>>
>> I'm sorry. I didn't mean to say recommend (in the RFC 2119 sense).  
>> I more
>> meant to say in keeping with WCAG advice. I should be more precise  
>> even in
>> my email messages.
>
> WCAG 2.0 does not advise that layout tables should have a null summary
> attribute. There is a technique that states that a null summary is
> acceptable [1], but does not advise that layout tables should use a
> null summary attribute.

OK. That's even more precise than I put it, and the sentiment is still  
the same.  Now with the greater precision you've provided, I'll repeat:

>> The substantive differences between version A and version B is that  
>> version
>> B recommends summary="" (null) for layout tables and also directs
>> authors to include a caption within 'summary' if the author elects  
>> to omit a
>> caption entirely (though prohibiting the use of 'summary' for  
>> caption when
>> the author includes 'caption' content). The idea here is that non- 
>> visual
>> users have a strong need for a caption even though captions can  
>> often be
>> omitted for visual users.
>
>
>

>> I think we should discourage the use of layout tables, but that we  
>> shouldn't
>> avoid guiding authors who use them (unless we're prepared to  
>> prohibit their
>> use and say "authors must not use layout tables").
>
> Authors should not be guided to provide a null summary attribute for
> layout tables. Layout tables shouldn't use any structural markup.

Do we need to rely solely on heuristics to determine which tables are  
layout and which are not when some authors will be eager to make the  
distinction explicitly? I think we do a disservice to non-visual users  
if we take such a strident approach.

> I agree with the WCAG 2.0 technique that a null summary attribute is
> acceptable on layout tables, but I don't agree that it's advisable
> (and WCAG 2.0 doesn't advise its use).

I'm not speaking about WCAG here. I'm suggesting that it is advisable  
to mark the use of layout tables explicitly, since it allows authors  
who need to resort to a single layout table to make that explicit in  
their markup rather than forcing AT to rely on heuristics.

>> I certainly don't want to contribute to the confusion between  
>> caption and
>> summary. Version B tries to reduce the confusion by being explicit  
>> about how
>> to craft summary and captions (and with Leif's section also a more  
>> complete
>> specification for crafting a caption). My view is that we only  
>> contribute to
>> the confusion by not addressing these issues.
>
> I think the HTML 5 specification should simply state the purpose of
> the summary attribute as unambiguously as possible, maybe with a
> simple example, and point to WCAG 2.0 for advice on how to use the
> summary attribute.

Part of stating unambiguously is filling in the holes where authors  
will be confused about what to do. One of those places is when an  
author, for whatever reason, feels the need to resort to a layout  
table. If we don't provide advice for this situation we do harm to AT  
users. The second place that leads to ambiguity is not telling authors  
what to do when they determine their visual users do not need a  
caption. If we don't want summary used for this purpose, then we  
should still state explicitly what authors should do in this  
situation. So an alternative might be to say that "if authors decide  
to omit a caption for visual users they should still include a caption  
using the caption element and use CSS (or something like XHTML2's  
media attribute) to conceal the caption from visual users". The point  
is that captions are often imperative for non-visual users when they  
are not as important or even superfluous for visual users. I'm simply  
trying to ensure we don't leave these holes in the document  
conformance criteria and I'm not trying to push a particular solution.  
I see the wiki as a simply a draft and a place to mold these solutions  
collectively.

>> I would certainly be happy to
>> see HTML5 say "authors should not use tables for layout", but I  
>> don't think
>> we have reached a level of specification nor support to be able to  
>> say
>> "authors must not use tables for layout" which is why WCAG  
>> addresses the
>> situation.
>
> WCAG 2.0 does not give advice about providing a summary attribute for
> layout tables. One of the techniques makes a passing reference to a
> null attribute being acceptable on layout tables (not recommended; not
> advisable; acceptable).

Agreed.I wasn't trying to claim any more than that. However, I do  
think it is something that HTML document conformance should address or  
we leave ambiguity that is harmful to some users. I simply want to  
make sure we address the problem of layout tables (though that might  
be done instead with another criterion such as perhaps prohibiting  
layout tables). Again, I feel it does harm to AT users to not address  
the situation.

>> My feeling is that version A is too ambiguous and will therefore
>> contribute to the confusion we're all trying to avoid.
>
> The wording might need improving to make suitable for inclusion in a
> specification, but I don't think version A is ambiguous about the
> purpose of the summary attribute. It clearly states the purpose of the
> summary attribute without confusing its purpose with other elements
> and without encouraging authors to provide structural markup for
> layout tables.

I wasn't really referring to the prose. I'm suggesting that leaving  
gaps in these particular situations and use cases (and there may be  
others) leads to ambiguity, however well written the prose. So my  
point is that if we do not address the omission of captions (which  
often aren't needed for visual users) and the continued though  
diminished use of layout tables, we leave ambiguity in the  
specification that is detrimental to disabled users and users of non- 
visual media.

Take care,
Rob

Received on Sunday, 1 March 2009 02:39:49 UTC