Rule-based Dependency Parse Collapsing and Propagation for German and English

We present a flexible open-source framework that performs dependency parsing with collapsed dependencies. The parser framework features a rule-based annotator that directly works on the output of a dependency parser. Thus, it can introduce dependency collapsing and propagation (de Marneffe et al., 2006) to parsers that lack this functionality. Collapsing is a technique for dependency parses where words, mainly prepositions, are elevated into the dependency relation name. Propagation assigns syntactic roles to all involved items in conjunctions. Currently, only the Stanford parser features these abilities for the English language. Here we introduce a rule-based collapsing engine that can be applied on top of the output of a dependency parser and that was used to re-engineer the rules of the English Stanford parser. Furthermore, we provide the first dependency parser with collapsing and propagation for German. We directly compare our collapsing for English with the one from the Stanford parser. Additionally, we evaluate collapsed and non-collapsed syntactic dependencies extrinsically when used as features for building a distributional thesaurus (DT).