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RE: Graphs and Alt Text

From: John Foliot <john@foliot.ca>
Date: Fri, 16 Nov 2012 13:25:51 -0800
To: "'Patrick H. Lauke'" <redux@splintered.co.uk>, <w3c-wai-ig@w3.org>
Message-ID: <002401cdc440$f61450d0$e23cf270$@ca>
Patrick H. Lauke wrote:
> On 16/11/2012 20:47, Daman Wandke wrote:
> > I am trying to figure out the best way to write alt text for line
> > graphs.  I am wondering what techniques others have used.  Graphs are
> > used to represent data quickly, but they also contain a lot of data.
> > How do I balance the amount of information?  I also have to find a
> > technique that content editors can implement easily.  The only
> technique
> > I can think of is to include an accessible data table with the data.
> > Looking forward to any input or suggestions.
> The traditional answer would indeed be to at least include the raw data
> in a correctly (with the right headers etc) marked up table. It would
> also be useful (for all users, including those that can see the graph
> itself) if there was a summary of what the graph was trying to
> illustrate, I'd say. A la "With the exception of Q1 2012, sales in the
> past year have been on a steady rise, closing at a total of $5bn, more
> than double the previous year's closing figure of $2.3bn" ... or
> something.

I'll also take this opportunity to mention that, under most circumstances this would also be a good candidate for @longdesc; following Patrick's recommendation, ensure that the data is also being made available in a table-based structure, which can benefit many users. If design considerations are such that you cannot visually provide that data table on the same page as the chart graphic, providing a link to an alternative page with the table data is the next best choice. 

This can be achieved via @longdesc, although that will (generally) only be available to screen reader users (the majority of which today provide support for @longdesc). For this reason, if there is room in the visual design to provide an on-screen text link to the second (table data) page, so that all users could follow the link, that this would be a beneficial and indeed better strategy.

I would also suggest that the summary text that Patrick proposed would be the appropriate @alt text for the image, followed on by the extended data linked elsewhere.


Received on Friday, 16 November 2012 21:26:27 UTC

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