Lexicalized Syntax and Topology for Non-projective Dependency Grammar

Abstract

We propose a lexicalized formulation of dependency grammar that addresses both immediate dependence and linear precedence. Our approach distinguishes two orthogonal, yet mutually constraining dependency trees: an ID tree of syntactic dependencies and a LP tree of topological dependencies. The ID tree is non-ordered, non-projective and its edges are labeled by grammatical functions. The LP tree is ordered and projective and expresses licensed linearizations; its edges are labeled by topological fields. The LP tree can be regarded as deriving from the ID tree through a process of emancipation controlled by lexicalized constraints and principles. In the present article, we formalize valid ID/LP analyses and show how they can be characterized as the solutions of a constraint satisfaction problem. The latter can be solved by constraint programming and forms the basis of our implementation.