Graph Transformations in Data-Driven Dependency Parsing
Nilsson, Nivre, & Hall use syntactic transformations to improve parsing performance on the Prague Dependency Treebank. Their first transform re-structures the dependency relationships used to encode conjunctions, essentially promoting the first conjunct to act as the head of the phrase (instead of the conjunction itself). The second transformation reverses the dependency direction between auxilliary verbs and main verbs. Both of these transformations essentially act by replacing dependencies on functional elements (conjunction words and auxilliliary words) with dependencies on their primary lexical elements.