Paper: Nested Named Entity Recognition

ACL ID D09-1015
Title Nested Named Entity Recognition
Venue Conference on Empirical Methods in Natural Language Processing
Session Main Conference
Year 2009

Many named entities contain other named entities inside them. Despite this fact, the field of named entity recognition has al- most entirely ignored nested named en- tity recognition, but due to technological, rather than ideological reasons. In this pa- per, we present a new technique for rec- ognizing nested named entities, by using a discriminative constituency parser. To train the model, we transform each sen- tence into a tree, with constituents for each named entity (and no other syntactic struc- ture). We present results on both news- paper and biomedical corpora which con- tain nested named entities. In three out of four sets of experiments, our model outperforms a standard semi-CRF on the more traditional top-level entities. At the same time, we improve the overall F-score by up t...