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RE: illustrating content - tables of figures

From: Charles McCathieNevile <charles@w3.org>
Date: Tue, 23 Jul 2002 13:30:28 -0400 (EDT)
To: "Chris O'Kennon" <chris@vipnet.org>
cc: WAI GL <w3c-wai-gl@w3.org>
Message-ID: <Pine.LNX.4.30.0207231318270.27750-100000@tux.w3.org>

One way to approach this for retrofitting is to find a way of making it
happen on a proxy. This is very low cost if pages are generated and then
stored (or cached by the server) although  there is a potential performance
hit that would mean a new design should build in the functionality.

The paper presented by Max Froumentin and Vincent Hardy shows how to use XSLT
to turn some XML data into an SVG histogram:

for the following data format:

<data>
<datum>23</datum>
<datum>94</datum>
<datum>55</datum>
</data>

which is simplistic but not terribly so, and an easy pattern to generate from
almost any content management system, the following XSLT

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
<xsl:template match="/">
<svg xmlns:svg="http://www.w3.org/2000/svg" viewBox="0 0 {10*(count(data/datum)+1)} 100">
<xsl:for-each select="data/datum">
<rect x="{10*position()}" y="{100- .}" width="10" height="{.}" fill="red" stroke="black"/>
</xsl:for-each>
</svg>
</xsl:template>
</xsl:stylesheet>

will produce a set of columns in an image the right size to contain them.
The image produced for the sample above is at
http://www.svgopen.org/papers/2002/froumentin_hardy__xslt/data.svg for the
curious. The sizing here is based on linear scales, - logarithmic scales
involve a little more work. And adding labelling of the table to make it more
directly accessible is also a couple of lines of extra work.

This is explained in the paper -
http://www.svgopen.org/papers/2002/froumentin_hardy__xslt/index.html#id2590086
and if you get fascinated there is an explanation of how to do the same for a
textual representation of a chess game (the sort of thing you find in
Newspapers near the sports and comics section) to have a nice animated view
of the game being played.

This can all be done by passing the page through a proxy after it has been
generated, as a last resort that isn't really horrendously hard. Or it can be
built in to the design to make it much easier.

Cheers

Charles McCN

On Tue, 23 Jul 2002, Chris O'Kennon wrote:

>This has been a rather long thread, so I apologize for missing the
>beginning.  But what level of conformance is this aspect being considered?
>I can see - on the development side - that this will be one that will be
>impractical in many cases.  If an application is designed to dynamically
>generate a table of data, retrofitting that application to create a graphic
>on-the-fly would be so costly as to be prohibitive.
>
>Chris O'Kennon
>Commonwealth of Virginia Webmaster/
>VIPNet Portal Architect
>www.myvirginia.org
>
>______________________________________
>"When people are free to do as they please,
>they usually imitate each other."
>
>
>-----Original Message-----
>From: Charles McCathieNevile [mailto:charles@w3.org]
>Sent: Tuesday, July 23, 2002 8:44 AM
>To: WAI GL
>Subject: illustrating content - tables of figures
>
>
>
>One area where it is helpful to illustrate, and where it is technically
>trivially easy in many cases is tables of numeric data. Programs to
>transform these into graphic representations have been available as
>mass-market software at least since 1990.
>
>I would suggest that one criteria is that all tables of numeric data are
>accompanied by a graphic representation.
>
>At the level of techniques, there is information I have read when I studied
>this stuff explaining different kinds of graphing techniques, and some
>results of testing the different ones for usability. If anyone has current
>knowledge and experience some references would be helpful.
>
>Charles McCN
>
>

-- 
Charles McCathieNevile    http://www.w3.org/People/Charles  phone: +61 409 134 136
W3C Web Accessibility Initiative     http://www.w3.org/WAI  fax: +33 4 92 38 78 22
Location: 21 Mitchell street FOOTSCRAY Vic 3011, Australia
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Received on Tuesday, 23 July 2002 13:31:21 GMT

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