On Equality Up-to Constraints over Finite Trees, Context Unification, and One-Step Rewriting

  title={On Equality Up-to Constraints over Finite Trees, Context Unification, and One-Step Rewriting},
  author={Joachim Niehren and Manfred Pinkal and Peter Ruhrberg},
We introduce equality up-to constraints over finite trees and investigate their expressiveness. Equality up-to constraints subsume equality constraints, subtree constraints, and one-step rewriting constraints. We establish a close correspondence between equality up-to constraints over finite trees and context unification. Context unification subsumes string unification and is subsumed by linear second-order unification. We obtain the following three new results. The satisfiability problem of… 
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