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Ordering Constraints on Trees

Hubert Comon; Ralf Treinen
DFKI, DFKI Research Reports (RR), Vol. 94-12, 1994.


We survey recent results about ordering constraints on trees and discuss their applications. Our main interest lies in the family of recursive path orderings which enjoy the properties of being total, well-founded and compatible with the tree constructors. The paper includes some new results, in particular the undecidability of the theory of lexicographic path orderings in case of a non-unary signature.