Pyramid: A Layered Model for Nested Named Entity Recognition

Jue Wang, Lidan Shou, Ke Chen, Gang Chen


Abstract
This paper presents Pyramid, a novel layered model for Nested Named Entity Recognition (nested NER). In our approach, token or text region embeddings are recursively inputted into L flat NER layers, from bottom to top, stacked in a pyramid shape. Each time an embedding passes through a layer of the pyramid, its length is reduced by one. Its hidden state at layer l represents an l-gram in the input text, which is labeled only if its corresponding text region represents a complete entity mention. We also design an inverse pyramid to allow bidirectional interaction between layers. The proposed method achieves state-of-the-art F1 scores in nested NER on ACE-2004, ACE-2005, GENIA, and NNE, which are 80.27, 79.42, 77.78, and 93.70 with conventional embeddings, and 87.74, 86.34, 79.31, and 94.68 with pre-trained contextualized embeddings. In addition, our model can be used for the more general task of Overlapping Named Entity Recognition. A preliminary experiment confirms the effectiveness of our method in overlapping NER.
Anthology ID:
2020.acl-main.525
Volume:
Proceedings of the 58th Annual Meeting of the Association for Computational Linguistics
Month:
July
Year:
2020
Address:
Online
Editors:
Dan Jurafsky, Joyce Chai, Natalie Schluter, Joel Tetreault
Venue:
ACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
5918–5928
Language:
URL:
https://aclanthology.org/2020.acl-main.525
DOI:
10.18653/v1/2020.acl-main.525
Bibkey:
Cite (ACL):
Jue Wang, Lidan Shou, Ke Chen, and Gang Chen. 2020. Pyramid: A Layered Model for Nested Named Entity Recognition. In Proceedings of the 58th Annual Meeting of the Association for Computational Linguistics, pages 5918–5928, Online. Association for Computational Linguistics.
Cite (Informal):
Pyramid: A Layered Model for Nested Named Entity Recognition (Wang et al., ACL 2020)
Copy Citation:
PDF:
https://aclanthology.org/2020.acl-main.525.pdf
Video:
 http://slideslive.com/38929230
Code
 LorrinWWW/Pyramid +  additional community code
Data
GENIANNE