Relationship between non-projective edges, their level types, and well-nestedness

Abstract

Dependency analysis of natural language gives rise to non-projective structures. The constraint of well-nestedness on dependency trees has been recently shown to give a good fit with empirical linguistic data. We present a reformulation of this constraint using properties of nonprojective edges and show its formal relationship to level types of non-projective edges; we also derive a simple O(n2) algorithm for checking well-nestedness.