3 ms·
I wonder if there's a general term in engineering for the case where a particular risk has been reduced well below the likelihood of more serious but exotic ris
by schoen 8y ago
I wonder if there's a general term in engineering for the case where a particular risk has been reduced well below the likelihood of more serious but exotic risks. I've heard about this most in cryptography where we can sometimes say that the risk of, say, a system failing due to an unexpected hash collision is drastically less than the risk of the system failing due to cosmic radiation or various natural disasters. At that point it doesn't seem important or worthwhile to consider this risk, because it's dwarfed by the others.
This seems like a form of the same argument, and I wonder where else this arises and how people describe it.
- matthewmcg 8y agoI think in other contexts, you might say that these signals are "below the noise floor."
- entropicdrifter 8y agoAs an audio engineer (as well as a dev), I definitely agree with this use of that phrase.
- matt4077 8y agoIt’s not a perfect match, but Rumsfeldian “unknown unknowns” come to mind. Specifically: every X-nines durability design will be compromised by some failure mode you didn’t think of.
- macintux 8y agoI tend to assume pessimistically that the durability design will itself cause a problem. Redundant switches to survive a hardware failure, e.g., strikes me as inviting trouble.
- jzwinck 8y agoIndeed. I once had critical systems routed via a large redundant Cisco switch which claimed to be 1+1. Turns out there was a single "supervisor" component which failed (after just a year or two) and made the pair of switches useless. Apparently the designer worked in a team where nobody does anything when the boss is out.
- schoen 8y agoI don't think unknown unknowns are what I'm thinking of here. In this case the argument involves a very specific risk, and sometimes a very specific lower bound for its probability. For example, in the hash collision case the argument says that it's not worth worrying about the (known) probability of a software error due to an unexpected hash collision because it's dominated by the (known) probability of a comparable error due to cosmic radiation. (The former probability can be calculated using the birthday paradox formula, and the latter has been characterized experimentally in different kinds of semiconductor chips.) This kind of argument doesn't rely on the idea that there are other risks that we can't identify or quantify. It's about comparing two failure modes that we did think of, in order to argue that one of them is acceptable or at least not worth further attempts to mitigate.
- fanpuns 8y agoAlthough Rumsfeld often gets credit for this statement, it has been around for a long time before him https://en.wikipedia.org/wiki/There_are_known_knowns https://en.wikipedia.org/wiki/There_are_known_knowns
- otakucode 8y agoI think Rumsfeld gets credit for it because he was using it in the most degenerate, disingeuous form possible. Rather than guarding against legitimate concerns and pursuing actual handling of potential issues, he was just trying to rationalize continuing policies that were demonstrably counterproductive. It's one thing to say there might be factors we don't know. It's another to day that simply because there might be such things, we should dedicate significant resources and lives to blindly flailing away under the assumption that it will help. A presumption of unknown unknowns puts you in a position of not acting, normally. There is no way to know that you aren't exacerbating and making a problem worse if you know that little.
- pixl97 8y agohttps://en.wikipedia.org/wiki/Black_swan_theory https://en.wikipedia.org/wiki/Black_swan_theory
- jorangreef 8y agohttps://en.wikipedia.org/wiki/Information_theory https://en.wikipedia.org/wiki/Information_theory