W3C home > Mailing lists > Public > public-html@w3.org > February 2009

Re: Caption@title instead of table@summary?

From: Leif Halvard Silli <lhs@malform.no>
Date: Wed, 18 Feb 2009 16:16:57 +0100
Message-ID: <499C2669.5050201@malform.no>
To: joshue.oconnor@cfit.ie
CC: HTMLWG <public-html@w3.org>
Joshue,

Joshue O Connor 2009-02-18 12.33:
> Leif Halvard Silli wrote:
>> This message investigate the option of replacing table@summary with
>> caption@title.
>>
>> The @title attribute is reserved for advisory information. But what
>> @title is supposed to advice about differs a bit from element to
>> element. For instance, for an anchor link (<a href="*">), the @title
>> attribute advices not on the content of the element, but on the content
>> of the link target - usually. For an <img>, the @title might inform on
>> who created the image.
>>
>> Hence, I wonder if the @title of the <caption> would be able to replace
>> @summary. After all, it seems reasonable to say that the @title of a
>> <caption> advices on what the <caption> is an caption for. Thus, a table
>> summary could fit there.
> 
> I don't think there is any need to go down this route as @summary could
> already provide this kind of additional advisory information if needed.
> Also there would be issues around implementing a new attribute in a UA,
> backwards compatibility and so on.

Since you mention "implementing a new attribute in a UA", then 
please note that when I said that "a table summary could fit 
here", then I meant that it could be possible to use the title 
attribute as a summary content container. I did not suggest any 
new attribute. (I assume that @title is supported *at least* as 
well as @summary in all user agents.)

But may be UAs would have to change how they treat the title of 
<caption>, in order to get it work the exact same way as 
@summary. And may be that is what you meant?

> There is currently nothing to stop an
> author putting additional advisory information into the @summary of the
> data table, as well as an overview of its structure. It can be as terse
> or verbose at the author deems fit and will be accessible by many many
> users of Assistive Technology.

The title attribute (of <caption>, at least) can contain: 5000 
chararacterss in Opera, unlimited amount characters in Firefox and 
Safari [though the screen hight put limits on display], but only 
around 256 characters in IE 7 to IE 8. I don't know wheter screen 
readerse are able to read longer title attributes than IE can 
display - if they can't, then @summary would be more screen reader 
compatible than @title. But if they can, then the technical issues 
with regard to lenght, should be the same.
  	
> Of course this is only possible if @summary is in the spec in the first
> place.
> 
> 
>> Benefits of using @summary:
>>
>>    * All UAs support @title - extremely backwards compatible. Doesn't
>>      require any CSS hoolahoops.
>>    * Like @summary, @title ensures that the content is purely fast
>>      accessible text.
>>    * All users can easily view @title content (mouse hovering is the
>>      typical way)
>>    * Empty <caption> elements are hidden, but still visible in the DOM.
>>    * Even empty <caption> elements can be made "visible" through
>>      relatively simple CSS and thus become available for hovering even
>>      for visuall user agents, so that @title content can be read even
>>      when <caption> is empty.
>>    * Could promote more use of (non-empty) <caption> elements, which
>>      should benefit all users.
>>    * The link between table summary and caption becomes clear.
>>    * Avoids the problems of the (claimed) misused @summary
>>    * Builds on common pattern, namely the use of the @title attribute
>>
>> AT software benefits and problems:
>>
>>    * Not each and every screen reader support @summary (Or am I wrong
>>      there?)
> 
> Pretty much all screen readers support @summary, including older
> versions which means there is already a vast audience of Assistive
> Technology users out there who can avail of it, today.

So, basically, support is for @summaryt in said UAs is more or 
less on pair with support for @title. That's a strong argument!

>>    * What about discoverability, eg when <caption> is empty?
> 
> If <caption> is empty the @summary contents are announced as soon as a
> table had focus. If the <caption> is populated then its contents are
> outputted. If both <caption> and @summary are populated the caption is
> announced first and the @summary follows. The user can end the
> outputting of either by changing focus to another HTML element.

So it sounds as if @summary is well integrated into how tables are 
treated, since UAs starts to read it immediately.

But what about @title? If there is no @summary while an empty 
<caption> with a non-empty @title attribute is present, would it 
then automatically read the title? I (now) assume that UAs would 
not start to read the title then. The  user would have to ask for 
it to be read. Am I right? If so then there would be a 
compatibility issue.

This is perhaps also why a <summary> element inside <caption> 
could work better than using the <caption> title: UAs would then 
start to read the <summary> element immediately, and user could 
turn this reading off easily if he/she wants.
-- 
leif halvard silli
Received on Wednesday, 18 February 2009 15:36:24 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Wednesday, 9 May 2012 00:16:31 GMT