- From: Joe Clark <joeclark@joeclark.org>
- Date: Fri, 24 Jan 2003 19:57:43 -0500 (EST)
- To: WAI-IG <w3c-wai-ig@w3.org>
> If you have access to the original data used to generate the graph Note: *Data*. Something difficult for humans to understand, which is why we draw graphs. > you > should be able to generate a textual explanation of it as well Here we go again. The WAI has a nasty habit of demanding that Web authors create labour-intensive and indeed useless derivative works; carries on as if such were even *possible* in the first place; and avoids doing the same dirty work itself. WAI has a master-slave relationship with authors: You struggle under the boulders so we can enjoy the pyramids. When it comes to long descriptions of charts and graphs, the requirement <http://www.w3.org/TR/WCAG10-HTML-TECHS/#long-descriptions> gives, as its *full and complete* example, only the following: <quoth> Example. <IMG src="97sales.gif" alt="Sales for 1997" longdesc="sales97.html"> In sales97.html: A chart showing how sales in 1997 progressed. The chart is a bar-chart showing percentage increases in sales by month. Sales in January were up 10% from December 1996, sales in February dropped 3%, .. End example. </quoth> Note well the ellipsis. WAI cannot even be bothered to *write out a genuine example* in *all* the detail they expect the rest of the world to provide. In part this is because WCAG is so tremendously poorly written. It's a fatuous and irrelevant idea anyway. To quote myself (Chapter 6, page 85): "like packing, unpacking, and repacking a suitcase, once some numbers are rendered graphically, it is not always easy or straightforward to re-render that graphic in numbers (and words)." I note that Charles rather revealingly uses the term "generate": "you should be able to generate a textual explanation." Like it's produced by a machine. Like it's even possible half the time. Also, "a textual explanation" is a clumsy, euphemistic way to demand that page authors *write coherent prose*, an ability WAI lacks. You know you're in trouble if you're being told to mount an impossible campaign, your leader shoulders none of the work, and your leader can't even be bothered to tell it to you straight. WAI members had at the time and possibly still have an incomplete, casual, anecdotal knowledge of the true nature of charts and graphs. (That's equally true for the true nature of *writing*, but we'll get to that another day.) If it were genuinely possible to transform many classes of *data* into *coherent prose*, we wouldn't use graphs in those cases. Some or even most of the time, it *is not possible* to transform data into a graph into prose-- *if* you want to retain even significant portions of the underlying meaning, let alone the myriad details that become visible in graphing. (I would point to scatter charts, error bars, outliers, and logarithmic scales as examples of *information* that is not clear from the underlying data and resists encapsulation in prose.) I'm not a huge fan of Edward Tufte's books, but here's a challenge for the WAI: Take ten examples from each of his volumes and "generate a textual explanation" of them. <http://www.edwardtufte.com/1176313877/tufte/books_vdqi> -- Joe Clark | joeclark@joeclark.org Author, _Building Accessible Websites_ <http://joeclark.org/access/> | <http://joeclark.org/book/>
Received on Friday, 24 January 2003 19:57:46 UTC