The Even More Liberalized δ–Rule in Free Variable Semantic Tableaux
نویسندگان
چکیده
In this paper we have a closer look at one of the rules of the tableau calculus presented in [3], called the δ–rule, and the modification of this rule, that has been proved to be sound and complete in [6], called the δ–rule, which uses fewer free variables. We show that an even more liberalized version, the δ + –rule, that in addition reduces the number of different Skolem–function symbols that have to be used, is also sound and complete. Examples show the relevance of this modification for building tableau–based theorem provers.
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