[Accessibility_sig] making RTG PNG files accessible

[Moore, Michael]

Jim,

Since the graphs are being generated on the fly from an external
webservice and the statistics that are being displayed in the graph are
also available from the webservice I would recommend the following
approach.

The alt text for the graph should probably be quite short, providing the
type of graph and the type of data presented. E.g. "Bar graph of site
traffic over the past twelve hours by web page."

Since you have the stats available, I would then autogenerate an
accessible tabular presentation of the data, and display the table on
the same page or link to it.  Displaying it on the same page would be
simpler programmatically.  This presentation would be helpful to all of
your users. 

Mike Moore
Accessibility Specialist
Department of Assistive and Rehabilitative Services (DARS)

"If you don't have time to do it right, 
when will you have time to fix it?"

-----Original Message-----
From: accessibility_sig-bounces at knowbility.org
[mailto:accessibility_sig-bounces at knowbility.org] On Behalf Of Jim Lyons
Sent: Monday, June 11, 2007 4:18 PM
To: accessibility_sig at knowbility.org
Subject: [Accessibility_sig] making RTG PNG files accessible

This is my first post here, so hello.  My name is Jim Lyons and I work
for the Office of Telecommunication Services at UT Austin.  I have a
question about generating and presenting graphs that display network
traffic that are accessible.

In order to monitor network traffic, we use a program called RTG, a
third-party C program that generates graphs as PNG files.  These graphs
display network traffic from a variety of viewpoints.  They are very
useful to our customers and we provide our customers a variety of
different graphs of their network traffic, including graphs generated
"on the fly", displaying up-to-the-minute data.

Unfortunately, these PNG files are totally inaccessible. Also, since
many of them are generated "on the fly" it is not possible to have
someone look at the graph and write an interpretive description of it.

I was thinking that the best way to make these graphs accessible
programmatically would be to capture descriptive statistics and output
them to files that my PHP program could read and use either as alt text
of longdesc files.  But I'm not sure which descriptive stats would be
best.
We could modify the code for RTG (not a pretty thought but doable) or
access the database ourselves with the same parameters sent to RTG, but
that would be prohibitively long for graphs covering long periods of
time (like a week or more).

Does anyone have any experience with this question?  I would appreciate
any helpyou might provide.

Thank you,

Jim Lyons


-----
Jim Lyons                     |  Operating Systems Specialist
OTS                           |  512-471-7414
University of Texas at Austin |  fax: 471-2449 jlyons at uts.cc.utexas.edu

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