Evaluating and Extending the Coverage of HPSG Grammars: A Case Study for German

Jeremy Nicholson; Valia Kordoni; Yi Zhang; Timothy Baldwin; Rebecca Dridan

In: Proceedings of the Sixth International Language Resources and Evaluation. International Conference on Language Resources and Evaluation (LREC-08), Marrakech, Morocco, ELRA, 5/2008.


In this work, we examine and attempt to extend the coverage of a German HPSG grammar. We use the grammar to parse a corpus of newspaper text and evaluate the proportion of sentences which have a correct attested parse, and analyse the cause of errors in terms of lexical or constructional gaps which prevent parsing. Then, using a maximum entropy model, we evaluate prediction of lexical types in the HPSG type hierarchy for unseen lexemes. By automatically adding entries to the lexicon, we observe that we can increase coverage without substantially decreasing precision.

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Deutsches Forschungszentrum für Künstliche Intelligenz
German Research Center for Artificial Intelligence