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by sharemywin 3029 days ago
I just regurgitation about some kind of article the professor brought in.

Wikipedia didn't exist when I was taking the course. It's probably in one of the 100 odd source articles since it wasn't just my professor that pointed it out. One of the other commenters mentioned a similar discussion from one of their professors.
1 comments
Jtsummers 3029 days ago
Fair. I wasn't replying to you, your #1 sounds a lot like what I'm saying, though.

  1. I remember hearing the system was only designed for
  XX operational hours but was being run over the
  operational spec.
This is very similar to my "at least" which is very different than "at most". In requirements we wouldn't bound ourselves like that. We wouldn't say our system should run for at most 8 hours. We'd say it should run for at least 8 hours. However, we won't say what happens after 8 hours because we don't test it (it's not a requirement). We may communicate to the operators that the system should be rebooted after some period of time if there's a known or anticipated issue, or we may include a soft boot to reset things. For many of our systems, their operating time is usually under 12 hours (they go on aircraft that don't fly for days at a time, mostly), so we never test anything past about 48 hours anyways. If there's an issue that arises around 96 hours, we'd never know from our testing and only know about if an operator pushed it to that limit and recorded the circumstances properly.
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sharemywin 3029 days ago
The Patriot system was originally designed to operate in Europe against Soviet medium- to high-altitude aircraft and cruise missiles traveling at speeds up to about MACH 2 (1500 mph). To avoid detection it was designed to be mobile and operate for only a few hours at one location.

http://archive.gao.gov/t2pbat6/145960.pdf

Page 2

I never did embedded programming or government programming, so what your saying make sense from a spec perspective.

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Jtsummers 3029 days ago
Right, but it didn't say that it was a cap on how long it should work correctly, rather it's a lower bound and also sets the maximum they tested it to. This is a design feature, but not a requirements feature, then, that it required a reboot after less than 8 hours of operations.
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