Re: How big could a bar code be if a bar code couldbe big?

From: Karl Auerbach <karl_at_cavebear_dot_com>
Date: Fri Apr 30 2004 - 19:50:36 CDT

> > I see in the archives a note that the maximum reliable bar code length is
> > 30 symbols - we are using 24 already. Each symbol gives about 6.5 bits of
> > information. So adding a message digest (32-bits) and ECC (8 bits?) means
> > about 7 more symbols - bringing us right up to, or even past, the maximum
> > and not leaving any room for bigger elections.
> >
> Maybe or maybe not. I'd still like to see some real data on ballot sizes.
> I think most ballots have fewer than 12 contests. I don't really know--this
> is only based on some light analysis I did a couple of years ago.

My own personal scaling alarms begin to tingle when I get to 10% of the
maximum. Given that our demo, even without a digital signature/message
digest and ECC is running at 80% usage of a 30 symbol EAN128C bar code my
scaling alarms are in full alert mode.

I did a quick web search of commercial bar-scanners and many of 'em now do
both 1d and 2d. So far my highly non-scientific search indicates PDF417
to be perhaps most widely supported. That survey has a confidence range
on the order of +/- 150%

By-the-way, USB cue-cats seem to work just fine, err, well, uh, let me
revise that to say that they work just as "fine" as keyboard port cue cats
normally do.

I've been digging through the code more and I think we need, for the
pilot, to adopt some coding standards to more clearly modularize data
containers (contests, ballots, etc) from the user interfaces. And we do
need to invent a layer of indirection to avoid embedding per-election
configuration into the code. This is beginning to suggest, to me, anyway,
that there might be a need for real database support, at least in the
configuration mechanisms.

                --karl--
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Received on Fri Apr 30 23:17:28 2004

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