There is a rule that says: “Avoid duplication of volatile information.”†. Disobedience of this rule may have disastrous consequences for an organization, whether it is just a computer system or a human society. Information — in the broadest sense of the word — that is widely diffused and then needs to be changed, may require a gigantic update operation, and — perhaps worse — may be unreliable or just wrong at all those places where the update operation has not been effectuated yet. (Changing all telephone numbers in the Netherlands, in the mid 1990s, was an enormous operation, which took a whole year. The transition of a lot of European currencies to the euro is an almost frightening prospect. The millennium problem, caused by an untraceable diffusion of an erroneous date field, will cost society billions and billions of dollars.)
KeywordsMutual Exclusion Proof Obligation Partial Correctness European Currency Interrupt Handler
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