more on Breathalyzers and Open Source

[David Farber <dave () farber net>]

Begin forwarded message:

From: Dennis Paull <dpaull () svpal org>
Date: October 24, 2005 3:21:52 PM EDT
To: David Farber <dave () farber net>
Subject: Re: [IP] Breathalyzers and Open Source


Hi Dave,

For IP if you wish.

I have written code for a Breathalyzer-like product as well as many  
other pieces of chemical measuring equipment
over a forty year career as an instrumentation design engineer. I  
suggest that viewing the source code will be
insufficient to determine how well the equipment works.

The key to any such equipment lies in the sensors being used, and the  
fact that sensors are seldom sensitive only to
the material being analyzed for, in this case ethyl alcohol. True,  
new sensor technology is advancing, but the equipment
in this case is intended to be produced at minimal cost and that  
often means using inexpensive hardware.

The sensors used in my work had many weaknesses:

1. Significant sensitivity to other chemicals that might occur in a  
persons breadth.

2. Significant sensitivity to ambient temperature and humidity.

3. Significant variations with time after equipment turnon.

4. Significant variations with the rate of exhalation of the breadth  
sample.

5. The fact that all these variables interacted.

Much of the software was an attempt to accommodate these variations.  
Additional sensors were used to
measure ambient conditions and remove these effects from the alcohol  
measurements. The success with
which these measurements accomplish their purpose will not be  
ascertained from examining the software,
only that the attempt was made.

Alas, the project that I put 18 months into was canceled due to the  
inability to find a feasible marketing
model. In our case, this was an ignition interlock device intended to  
keep drunks from starting their car.
That product market has remained small for a variety of reasons, but  
the measurement of breadth alcohol
was very similar to what was called a Breathalyzer at that time (over  
a decade ago).

I mention all these factors because they are common in many  
measurement instruments. To truly determine
the quality of any instrument's results, it is necessary to evaluate  
the whole package as a black box. This is
a difficult task for the reasons stated above, but is the only way to  
find out if the equipment actually works.
No amount of viewing the code will tell you that.

Dennis Paull
Half Moon Bay, CA 94019

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
~~~

David Farber wrote:


> Subject:
> [IP] Breathalyzers and Open Source
> From:
> David Farber <dave () farber net>
> Date:
> Mon, 24 Oct 2005 07:41:38 -0400
> To:
> Ip Ip <ip () v2 listbox com>
>
> To:
> Ip Ip <ip () v2 listbox com>
>
>
>
>
> Begin forwarded message:
>
> From: EEkid () aol txt
> Date: October 23, 2005 10:32:48 PM EDT
> To: dave () farber net
> Subject: Breathalyzers and Open Source
>
>
>
>
> Breathalyzers and Open Source
>
> Friday October 21, 2005 by Edward W. Felten
>
> Lawyers for 150 Floridians accused of drunk driving have asked a  
> court to order the disclosure of the source code for software  
> running in the breathalyzer machines used by police to analyze  
> their blood alcohol level, according to a Tom Sanders story on vunet.
>
> The defendants say they have the right to examine the machines that  
> accused them, and that a meaningful examination requires access to  
> the machines’ software. Prosecutors say the code is a trade secret.
>
> The accused are right that one needs the code to understand fully  
> how the machines work. The machines consist of sensors, a user  
> interface, and control software. The software is the “brain” of the  
> machine, and it is almost certainly involved in the calculations  
> that derive a blood alcohol value from the sensor readings, as well  
> as the display of the calculated value. If the accused have the  
> right to fully examine the machines — and the article says that  
> they do under Florida law — then they should see the source code.
>
> Contrary to the article and some other commentators, this is not a  
> dispute over whether the software should be open source. The  
> accused aren’t seeking to open the software to everybody; they only  
> want it opened to their legal teams.
>
> There are standard practices for handling trade-secret information  
> that must be turned over in court cases. A court will typically  
> establish a protective order, which is a kind of nondisclosure  
> agreement covering secret material that is turned over by one side  
> to the other. The protective order will require parties to keep the  
> information secret and to use it only for purposes related to the  
> court proceedings. Typically the information can be turned over to  
> a limited number of expert analysts who have also signed the  
> protective order. Documents containing secret information are filed  
> under seal, and testimony about secret matters may take place in a  
> closed courtroom.
>
> So this issue is not about open source, but about ensuring fairness  
> for the accused. If they’re going to be accused based on what some  
> machine says, then they ought to be allowed to challenge the  
> accuracy of the machine. And they can’t do that unless they’re  
> allowed to know how the machine works.
>
> You might argue that the machine’s technical manuals convey enough  
> information. Having read many manuals and examine the innards of  
> many software systems, I’m skeptical of such claims. Often, knowing  
> how the maker says a machine works is a poor substitute for knowing  
> how it actually works. If a machine is flawed, it’s likely the  
> maker will either (a) not know about the flaw or (b) be unwilling  
> to admit it exists.
>
> If the article’s description of Florida law is correct, this seems  
> like a pretty easy decision for the court.
>
> http://www.freedom-to-tinker.com/?p=914





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