Underspecified computation of normal forms

We consider the problem of computing, out of a set C of trees and a rewrite system R, those trees in C that cannot be rewritten into a tree in C. We solve this problem for sets of formulas that are described by dominance graphs, and a certain class of rewrite systems that we use to approximate entailment, and show how to compute the irreducible trees efficiently by intersecting tree automata. Our algorithm solves a 25-year-old problem in computational linguistics.

• Type: Conference
• Year: 2010
• Where: RTA
• Authors: Alexander Koller, Stefan Thater
• Keywords: Dominance Graphs, Irreducible Trees, Rewrite System R, RTA 2010, Theoretical Computer Science