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Re: table caption as a short description, @summary as a long description

From: Leif Halvard Silli <lhs@malform.no>
Date: Tue, 17 Feb 2009 04:29:20 +0100
Message-ID: <499A2F10.603@malform.no>
To: Steven Faulkner <faulkner.steve@gmail.com>
CC: Dan Connolly <connolly@w3.org>, "Gregory J. Rosmaita" <oedipus@hicom.net>, HTML WG <public-html@w3.org>, Matt Morgan-May <mattmay@adobe.com>
Steven Faulkner 2009-02-13 18.26:
> Hi dan ,
> in yesterdays HTML WG telecon you were questioning Gregory's idea of 
> @summary being a long descriptor and wondering where it came from:
> 
> "Each table may have an associated caption (see the CAPTION element) 
> that provides a short description of the table's purpose. A longer 
> description may also be provided (via the summary attribute) for 
> the benefit of people using speech or Braille-based user agents." 

So HTML 4 sees @summary as "long <caption>". Wheras WCAG 2, per 
Matt Morgan-May, view @summary as "not any <caption> at all":

[1] "The Techniques for WCAG 2 specify that <caption>
      and @summary should not duplicate one another. [...]
      It's also not intended to be visible, because
      it's intended as metadata to describe the structure
      of the table. Requiring it to be visible makes as
      much sense as making @alt visible."

It is easier to understand why it makes no sense to make @summary 
visible if we consider it as a long <caption>: It makes sense to 
render only one <caption>.

That way @summary also becomes directly comparable to HTML 4's 
abbr attribute: Where @summary provides long <caption>, @abbr 
provides a caption like version of the header cell[2]. Even if 
@abbr is also intended for visual UAs (small screens anyone?), 
both attributes provide a longer/shorter version of another 
element, for the purpose of serving different media types better.

As to the argument that if @summary is any useful, then it is also 
useful for sighted users: This might indeed be the case, and 
through DOM scripting, it is possible to make the content of any 
attribute visible. But as @abbr shows: It is also a useful to keep 
things short.

Following Ian's advice to give feedback in the form "as defined, I 
can't do this with HTML5"[3]:

Both <caption> and @summary provides metadata. But currently, in 
HTML 5, one cannot author the table metadata with both screen 
readers and visual media in mind, simply because, in visual 
medias, a long and wordy caption would not work or serve its 
purpose as caption. Such <caption>s would not even work for screen 
readers, since those readers too need short, clue giving captions. 
(As soon as one learns what a particular table is about, the 
@summary looses more if its purpose, while the short <caption> 
increases its usefullness.)

Thus, HTML 5 as defined does not let us provide users with fast 
accessed and fast read summaries of tables for the situations when 
the <caption> does not give the reader enough clue about what the 
table is about, when starting to wade through the table itself to 
find this out, would be considerably more timeconsuming than 
reading a such description.

HTML 5, as defined, also does not ofer any way for providing any 
such table spesific metatada *without* also adding a <caption>. 
(Authors may feel that not all tables *needs* a any <caption>. 
However, non-visual media users could benefit from a summary 
function even in those cases.)

Strictly speaking, a summary feature could be useful for all media 
types, if there were a cross-media method for providing it. 
Perhaps as a <summary> child element of <caption>? However, then 
one would need tom make <caption> a required element. See testcase 
for <summary> inside <caption> in Live DOM viewer. [4]

[1] http://www.w3.org/mid/C5AE130E.14131%25mattmay@adobe.com
[2] http://www.w3.org/TR/html401/struct/tables.html#adef-abbr
[3] http://lists.w3.org/Archives/Public/public-html/2008Dec/0175.html
[4] http://tinyurl.com/tableWithSummaryElement
-- 
leif halvlard silli
Received on Tuesday, 17 February 2009 03:30:08 GMT

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