Gordon Beaton wrote:
On Fri, 08 Feb 2008 09:57:33 +0100, Philipp wrote:
Daniel Pitts wrote:
Case and point, there was once an automated medical scanning device
that
worked 99.9% of the time, but there were a few accidents that no one
could figure out what happened. A few patients died from over-exposure
to radiation. This product of course had been extensively tested and
retested, and worked for so much of the time, but due to a race
condition it could fail (catastrophically) in an unexpected way.
I'd be interested in a reference for that. Can you remember where you
read it?
http://en.wikipedia.org/wiki/Therac-25 summarizes and has links to
further reading, all of it interesting.
Actually the manufacturer *claimed* that it had been extensively
tested, but that wasn't really the case.
The original article describing the details of the case was published in
the IEEE publication /Computer/ in the early 90s, IIRC. (The article is
referenced from the Wikipedia link.) It was written in a dry,
dispassionate and objective style that made the account all the more
chilling for its refusal to sensationalize.
The manufacturer didn't start claiming that it fixed the problem until
enough people found out that there was a problem; originally they
suppressed the information. Once they were called to account, they were
fond of rapidly responding with bizarre claims like "reliability has
been improved 5000%". Aside from the meaninglessness of such statements
absent any baseline measurement of "reliability", it is clear the
manufacturer actually did nothing to solve the problem except try to
hide it and let people die.