Dependency trees and the strong generative capacity of CCG

Abstract

We propose a novel algorithm for extracting dependencies from the derivations of a large fragment of CCG. Unlike earlier proposals, our dependency structures are always tree-shaped. We then use these dependency trees to compare the strong generative capacities of CCG and TAG and obtain surprising results: Both formalisms generate the same languages of derivation trees - but the mechanisms they use to bring the words in these trees into a linear order are incomparable. © 2009 Association for Computational Linguistics.