Special section: Information Retrieval and Natural Language Processing

 

Improving Named Entity Extraction Accuracy using Unlabeled Data and Several Extractors

 

Tomoya Iwakura and Seishi Okamoto

 

Fujitsu Laboratories Ltd., 1–1, Kamikodanaka 4–chome, Nakahara–ku, Kawasaki 211–8588, Japan. (iwakura.tomoya@jp.fujitsu.com, seishi@jp.fujitsu.com)

 

Manuscript received November 4, 2008.
Manuscript accepted for publication August 25, 2009.

 

Abstract

This paper proposes feature augmentation methods using unlabeled data and several Named Entity (NE) extractors. We collect NE–related information of each word (which we call NE–related labels) from unlabeled data by using NE extractors. NE–related labels which we collect include candidate NE class labels of each word and NE class labels of co–occurring words. To accurately collect the NE–related labels from unlabeled data, we consider methods to collect NE–related labels by using outputs of several NE extractors. We use NE–related labels as additional features for creating new NE extractors. We apply our NE extraction methods using the NE–related labels to IREX Japanese NE extraction task. The experimental results show better accuracy than the previous results obtained with NE extractors using handcrafted resources.

Key words: Named entity recognition, unlabeled data, combination of extractors.

 

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