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arXiv cs/9809014cs.LO
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经典逻辑中的一致可证性

Uniform Provability in Classical Logic

Gopalan Nadathur

摘要:

统一证明是微积分证明,具有以下特点:在证明的任何阶段,推导复杂公式的最后一步总是引入该公式的顶级逻辑符号。我们调查的相关性,这种统一的证明概念,在经典逻辑结构证明搜索。一种逻辑语言,其上下文可证明性等价于统一可证明性,它允许一个目标导向的证明过程,将逻辑符号解释为搜索指令,其含义由相应的推理规则给出。虽然这种统一的可证明性属性不直接适用于经典逻辑,但我们证明它适用于它的一个片段,该片段仅在对假设集进行适度的、合理的修改时排除全称量词的基本上为正的出现:向它们添加被证明的公式的否定。我们进一步注意到,所有使用添加的公式都可以分解为某些派生规则。由此产生的证明系统和统一的可证明性属性,它持有的是用来概述经典逻辑的证明过程。这个证明过程的一个有趣的方面是,它包含了以前提出的处理假设中的析取信息和处理假设的机制。我们的分析揭示了这些机制和统一证明的概念之间的关系。

英文摘要:

Uniform proofs are sequent calculus proofs with the following characteristic: the last step in the derivation of a complex formula at any stage in the proof is always the introduction of the top-level logical symbol of that formula. We investigate the relevance of this uniform proof notion to structuring proof search in classical logic. A logical language in whose context provability is equivalent to uniform provability admits of a goal-directed proof procedure that interprets logical symbols as search directives whose meanings are given by the corresponding inference rules. While this uniform provability property does not hold directly of classical logic, we show that it holds of a fragment of it that only excludes essentially positive occurrences of universal quantifiers under a modest, sound, modification to the set of assumptions: the addition to them of the negation of the formula being proved. We further note that all uses of the added formula can be factored into certain derived rules. The resulting proof system and the uniform provability property that holds of it are used to outline a proof procedure for classical logic. An interesting aspect of this proof procedure is that it incorporates within it previously proposed mechanisms for dealing with disjunctive information in assumptions and for handling hypotheticals. Our analysis sheds light on the relationship between these mechanisms and the notion of uniform proofs.

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