The STO-problem is NP-hard
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Krzysztof R. Apt; Peter van Emde Boas; Angelo Welling
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Article
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1994
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Elsevier Science
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English
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A finite set of term equations \(E\) is called subject to the occur-check (STO) if a sequence of actions of the Martelli-Montanari unification algorithm starts with \(E\) and ends with a failure due to occur-check. We prove here that the problem of deciding whether \(E\) is STO is NP-hard.