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Electronic Colloquium on Computational Complexity

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REPORTS > KEYWORD > ALTERNATION HIERARCHY:
Reports tagged with alternation hierarchy:
TR07-008 | 27th November 2006
Philipp Weis, Neil Immerman

Structure Theorem and Strict Alternation Hierarchy for FO^2 on Words

It is well-known that every first-order property on words is expressible
using at most three variables. The subclass of properties expressible with
only two variables is also quite interesting and well-studied. We prove
precise structure theorems that characterize the exact expressive power of
first-order logic with two variables on words. ... more >>>




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