arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2007.05459cs.LO
收藏

一阶逻辑有限类和前缀类的扩张保持

Extension Preservation in the Finite and Prefix Classes of First Order Logic

Anuj Dawar, Abhisekh Sankaran

摘要:

众所周知,经典的保序定理在有限域中是失败的:在一阶逻辑的存在片段中,有一些在扩张下封闭的有限结构的一阶可定义类是不可定义的(在有限域)。我们加强了这一点,为每个$n$,一阶可定义类的有限结构封闭的扩展下,是不可定义的$n$量词交替。我们构造的类是可定义的,在扩展的Datasheet与否定,实际上在传递闭包逻辑的存在片段。这否定了Rosen和Weinstein提出的一个开放性问题。

英文摘要:

It is well known that the classic Łoś-Tarski preservation theorem fails in the finite: there are first-order definable classes of finite structures closed under extensions which are not definable (in the finite) in the existential fragment of first-order logic. We strengthen this by constructing for every $n$, first-order definable classes of finite structures closed under extensions which are not definable with $n$ quantifier alternations. The classes we construct are definable in the extension of Datalog with negation and indeed in the existential fragment of transitive-closure logic. This answers negatively an open question posed by Rosen and Weinstein.

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。

↑