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Table summary, caption, and title

From: Wendy A Chisholm <wendy@w3.org>
Date: Mon, 24 Jan 2000 13:48:28 -0500
Message-Id: <4.2.0.58.20000124132730.00a21ac0@localhost>
To: w3c-wai-gl@w3.org
Cc: w3c-wai-er-ig@w3.org
Hello,

The ER WG would like clarification on the differences of the following 
TABLE attributes: "summary" and "title" and the CAPTION element.

The HTML 4 spec [1] says:
<BLOCKQUOTE>
summary = text [CS]
This attribute provides a summary of the table's purpose and structure for 
user agents rendering to non-visual media such as speech and Braille.

title = text [CS]
This attribute offers advisory information about the element for which it 
is set.

When present, the CAPTION element's text should describe the nature of the 
table. The CAPTION element is only permitted immediately after the TABLE 
start tag. A TABLE element may only contain one CAPTION element.

Visual user agents allow sighted people to quickly grasp the structure of 
the table from the headings as well as the caption. A consequence of this 
is that captions will often be inadequate as a summary of the purpose and 
structure of the table from the perspective of people relying on non-visual 
user agents.

Authors should therefore take care to provide additional information 
summarizing the purpose and structure of the table using the summary 
attribute of the TABLE element. This is especially important for tables 
without captions. Examples below illustrate the use of the summary attribute.
</BLOCKQUOTE>

The WCAG techniques document [2] says:
<BLOCKQUOTE>
Provide a caption via the CAPTION element.
Provide a summary via the "summary" attribute. Summaries are especially 
useful for non-visual readers.
</BLOCKQUOTE>

The following examples are given:
<BLOCKQUOTE>
<TABLE border="1"
           summary="This table charts the number of
                    cups of coffee consumed by each senator,
                    the type of coffee (decaf or regular),
                    and whether taken with sugar.">
      <CAPTION>Cups of coffee consumed by each senator</CAPTION>
</BLOCKQUOTE>

The ER working group has the following questions:

What structural information is supposed to be included in the summary:
1. notification of nested tables?
2. notification of spanning cells?
3. number of rows, columns?

If we assume a DOM is available, then at least 3 is easily available.  Are 
1 and 2?

Or does the content of summary describe what the structure does not reveal. 
the intended content. the larger semantic in which this table fits?  for 
example, "summary" could suggest that you have 5 income categories and 4 
expense categories.  In this example, there are most likely 9 columns each 
with an expense or income heading.  there are also two other headings, one 
that spans 5 columns ("Income") and one that spans 4 columns ("Expenses").

Can we draw parallels between alt and longdesc for images?  Is CAPTION like 
"alt" and "summary" like "londesc"?  If so, where does "title" fit into the 
picture?

If you provide a "summary" do you also need to provide a CAPTION?

Are both optional or are they both recommended?  WCAG Checkpoint 5.5 says 
"Provide summaries for tables" (P3) with "summary" as the example way to do 
it.  It seems that this checkpoint could apply to both "summary" and CAPTION.

Thoughts?

--wendy

[1] http://www.w3.org/TR/REC-html40/struct/tables.html
[2] http://www.w3.org/TR/1999/WAI-WEBCONTENT-TECHS-19990505/#tables
--
wendy a chisholm
world wide web consortium
web accessibility initiative
madison, wi usa
tel: +1 608 663 6346
/--
Received on Monday, 24 January 2000 13:46:55 GMT

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