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arXiv 2201.09969cs.LO
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一元一元二阶逻辑

Monadic Monadic Second Order Logic

Mikołaj Bojańczyk, Bartek Klin, Julian Salamanca

摘要:

正则语言与一元二阶逻辑对应的主要原因之一是正则语言类在满射字母到字母同态的象下是封闭的。这个闭包性质适用于有限字、有限树、无限字、无限树、自由群的元素等结构。在本文中,我们研究了哪些结构(通过集合范畴中的单子理解)使得正则语言(即由有限代数识别的语言)类在满射字母到字母同态的直接像下是封闭的。我们给出了单子满足这一性质的各种充分条件。我们还提出了许多单子的例子,包括不满足我们的充分条件的正面例子,以及闭包属性失败的反例。

英文摘要:

One of the main reasons for the correspondence of regular languages and monadic second-order logic is that the class of regular languages is closed under images of surjective letter-to-letter homomorphisms. This closure property holds for structures such as finite words, finite trees, infinite words, infinite trees, elements of the free group, etc. Such structures can be modelled using monads. In this paper, we study which structures (understood via monads in the category of sets) are such that the class of regular languages (i.e. languages recognized by finite algebras) are closed under direct images of surjective letter-to-letter homomorphisms. We provide diverse sufficient conditions for a monad to satisfy this property. We also present numerous examples of monads, including positive examples that do not satisfy our sufficient conditions, and counterexamples where the closure property fails.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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