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Title Order-Invariant Types and Their Applications
Authors Pablo Barceló, Leonid Libkin
Publication date April 2016
Abstract Our goal is to show that the standard model-theoretic
concept of
types can be applied in the study of order-invariant properties, i.e.,
properties definable in a logic in the presence of an auxiliary order
relation, but not actually dependent on that order relation. This is
somewhat surprising since order-invariant properties are more of a
combinatorial rather than a logical object. We provide two applications of
this notion. One is a proof, from the basic principles, of a theorem by
Courcelle stating that over trees, order-invariant MSO properties are
expressible in MSO with counting quantifiers. The other is an analog of the
Feferman-Vaught theorem for order-invariant properties.
Pages Article 9
Volume 12
Journal name Logical Methods in Computer Science
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