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arXiv 1212.6567cs.LOcs.CC
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L-递归与对数空间的一种新逻辑

L-Recursion and a new Logic for Logarithmic Space

Martin Grohe, Berit Grußien, André Hernich, Bastian Laubner

摘要:

我们扩展一阶逻辑计数的一个新的运营商,使其能够正式的有限形式的递归,可以在对数空间进行评估。由此产生的逻辑LREC具有LOGSPACE中的数据复杂性,并且它定义了LOGSPACE完全问题,如确定性可达性和布尔公式求值。我们证明了LREC的严格表达能力比具有计数的确定性传递闭包逻辑更强,而与对称传递闭包逻辑STC和传递闭包逻辑(有或没有计数)的表达能力是不可比拟的。LREC严格包含在具有计数FPC的定点逻辑中。我们还研究了LREC的一个扩展LREC=,它具有更好的闭包性质,比LREC和STC更有表现力,但仍然包含在FPC中,并且在LOGSPACE中具有数据复杂度。我们的主要结果是,LREC捕获LOGSPACE类的有向树和LREC=捕获LOGSPACE类的区间图。

英文摘要:

We extend first-order logic with counting by a new operator that allows it to formalise a limited form of recursion which can be evaluated in logarithmic space. The resulting logic LREC has a data complexity in LOGSPACE, and it defines LOGSPACE-complete problems like deterministic reachability and Boolean formula evaluation. We prove that LREC is strictly more expressive than deterministic transitive closure logic with counting and incomparable in expressive power with symmetric transitive closure logic STC and transitive closure logic (with or without counting). LREC is strictly contained in fixed-point logic with counting FPC. We also study an extension LREC= of LREC that has nicer closure properties and is more expressive than both LREC and STC, but is still contained in FPC and has a data complexity in LOGSPACE. Our main results are that LREC captures LOGSPACE on the class of directed trees and that LREC= captures LOGSPACE on the class of interval graphs.

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