On Uni cation Problems in Restricted Second-Order Languages
نویسندگان
چکیده
We review known results and improve known boundaries between the decidable and the undecidable cases of second-order uniication with restrictions on the number, the number of occurrences, and the arity of second-order variables. As a key tool we prove an unde-cidability result that provides a partial solution to an open problem regarding decidability of simultaneous rigid E-uniication with two rigid equations.
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