Comment:
From http://lists.w3.org/Archives/Public/public-comments-wcag20/2006May/0120.html
Text alternatives
And now, the biggest failure of the section on text equivalents. I've been warning WCAG Working Group about this topic for years. The fact that the following example made it this far into the writing process demonstrates that the Working Group simply will not accept reality.
A data chart: 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 comparable to that available from the chart, and provides the data in a table. It is obviously a lost cause to try to explain to WCAG that diagrams and data are not interchangeable. We create diagrams because data are too hard to understand. 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. Moreover, some data can be understood only if transformed (as by plotting on a logarithmic scale), which is the sort of thing that simply cannot be expressed understandably in numbers. I am aware that the National Braille Association has authorized WAI to publish parts of its training manual concerning the rendition of charts and graphs in audiobooks. I have seen no evidence that those techniques are viable on the Web. Given that they seem to work fine for audiobooks, I would be interested to see any such evidence.
The working group agrees that it may not always be possible or practical to provide access to the data. We also require a long description for this type of chart. We did not however mention that in the example - and that was an oversight. We have updated the example text to explain that a high-level summary of the data and applicable trends is provided in the long description.
The example has been revised as follows:
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.