Parser evaluation and the BNC: evaluating 4 constituency parsers with 3 metrics
Foster, Jennifer and van Genabith, Josef (2008) Parser evaluation and the BNC: evaluating 4 constituency parsers with 3 metrics. In: LREC 2008 - Sixth International Conference on Language Resources and Evaluation, 28-30 May 2008, Marrakech, Morocco.
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We evaluate discriminative parse reranking and parser self-training on a new English test set using four versions of the Charniak parser and a variety of parser evaluation metrics. The new test set consists of 1,000 hand-corrected British National Corpus parse trees. We directly evaluate parser output using both the Parseval and the Leaf Ancestor metrics. We also convert the hand-corrected and parser
output phrase structure trees to dependency trees using a state-of-the-art functional tag labeller and constituent-to-dependency conversion tool, and then calculate label accuracy, unlabelled attachment and labelled attachment scores over the dependency structures. We find that reranking leads to a performance improvement on the new test set (albeit a modest one). We find that self-training using BNC data leads to significantly better results. However, it is not clear how effective self-training is when the training material comes from the North American News Corpus.
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