How Bad Is The Problem Of PP-Attachment? A Comparison Of English, German And Swedish

The correct attachment of prepositional phrases (PPs) is a central disambiguation problem in parsing natural languages. This paper compares the baseline situation in English, German and Swedish based on manual PP attachments in various treebanks for these languages. We argue that cross-language comparisons of the disambiguation results in previous research is impossible because of the different selection procedures when building the training and test sets. We perform uniform treebank queries and show that English has the highest noun attachment rate followed by Swedish and German. We also show that the high rate in English is dominated by the preposition of. From our study we derive a list of criteria for profiling data sets for PP attachment experiments.