[Bug 23291] Add statements about when longdesc is inappropriate

https://www.w3.org/Bugs/Public/show_bug.cgi?id=23291

--- Comment #1 from Laura Carlson <laura.lee.carlson@gmail.com> ---
An accessible table is usually inefficient for graphics of tabular data.

Something to keep in mind is that, 1.) data visualizations and  2.) long
descriptions of data visualizations have the same aim but have typically served
different audiences. 

1.) The aim of data visualizations (charts and graphs) has typically been to
make data easier to understand to sighted people rather than simply providing
raw data in a table.

2.) The aim of long descriptions of data visualizations has typically been to
make the data easier to understand to people with disabilities rather than
simply providing raw data in a table.

Notice both aims are to *understand data*. Providing the data itself with
either number one or number two is a nice touch but it is not the primary aim
of either.

Joe Clark talked about this some years ago in a WCAG comment [1]. He said,
"To use an analogy over again, diagrams and data are like a suitcase that can
be unpacked but not easily repacked. If data were understandable by themselves,
we wouldn't make a chart. I can assure the Working Group that giving
nondisabled people a really nice chart and disabled people a table with 10,000
or more data points does not constitute equality in any sense."

WCAG revised their example after his comment to read: "A bar chart compares how
many widgets were sold in June, July, and August. The short label says, 'Figure
one - Sales in June, July and August.' The longer description identifies the
type of chart, provides a high-level summary of the data, trends and
implications comparable to those available from the chart. Where possible and
practical, the actual data is provided in a table."

[1]
https://www.w3.org/2006/02/lc-comments-tracker/35422/understandingwcag20/789

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Received on Tuesday, 10 December 2013 12:57:40 UTC