Enhancing Performance of Lexicalised Grammars

This paper describes how external resources can be used to improve parser performance for heavily lexicalised grammars, looking at both robustness and efficiency. In terms of robustness, we try using different types of external data to increase lexical coverage, and find that simple POS tags have the most effect, increasing coverage on unseen data by up to 45%. We also show that filtering lexical items in a supertagging manner is very effective in increasing efficiency. Even using vanilla POS tags we achieve some efficiency gains, but when using detailed lexical types as supertags wemanage to halve parsing time with minimal loss of coverage or precision.