Named Entity Recognition with Partially Annotated Training Data
Stephen D. Mayhew, Snigdha Chaturvedi, Chen-Tse Tsai, Dan Roth · 2019
Supervised machine learning assumes the availability of fully-labeled data, but in many cases, such as low-resource languages, the only data available is partially annotated.We study the problem of Named Entity Recognition (NER) with partially annotated training data in which a fraction of the named entities are labeled, and all other tokens, entities or otherwise, are labeled as non-entity by default.In order to train on this noisy dataset, we need to distinguish between the true and false negatives.To this end, we introduce a constraintdriven iterative algorithm that learns to detect false negatives in the noisy set and downweigh them, resulting in a weighted training set.With this set, we train a weighted NER model.We evaluate our algorithm with weighted variants of neural and non-neural NER models on data in 8 languages from several language and script families, showing strong ability to learn from partial data.Finally, to show real-world efficacy, we evaluate on a Bengali NER corpus annotated by non-speakers, outperforming the prior state-of-the-art by over 5 points F1.