Parser Showdown at the Wall Street Corral: An Empirical Investigation of Error Types in Parser Output

Constituency parser performance is primarily interpreted through a single metric, F-score on WSJ section 23, that conveys no linguistic information regarding the remaining errors. We classify errors within a set of linguistically meaningful types using tree transformations that repair groups of errors together. We use this analysis to answer a range of questions about parser behaviour, including what linguistic constructions are difficult for stateof-the-art parsers, what types of errors are being resolved by rerankers, and what types are introduced when parsing out-of-domain text.