A Novel Cascade Binary Tagging Framework for Relational Triple Extraction

Zhepei Wei, Jianlin Su, Yue Wang, Yuan Tian, Yi Chang


Abstract
Extracting relational triples from unstructured text is crucial for large-scale knowledge graph construction. However, few existing works excel in solving the overlapping triple problem where multiple relational triples in the same sentence share the same entities. In this work, we introduce a fresh perspective to revisit the relational triple extraction task and propose a novel cascade binary tagging framework (CasRel) derived from a principled problem formulation. Instead of treating relations as discrete labels as in previous works, our new framework models relations as functions that map subjects to objects in a sentence, which naturally handles the overlapping problem. Experiments show that the CasRel framework already outperforms state-of-the-art methods even when its encoder module uses a randomly initialized BERT encoder, showing the power of the new tagging framework. It enjoys further performance boost when employing a pre-trained BERT encoder, outperforming the strongest baseline by 17.5 and 30.2 absolute gain in F1-score on two public datasets NYT and WebNLG, respectively. In-depth analysis on different scenarios of overlapping triples shows that the method delivers consistent performance gain across all these scenarios. The source code and data are released online.
Anthology ID:
2020.acl-main.136
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:
1476–1488
Language:
URL:
https://aclanthology.org/2020.acl-main.136
DOI:
10.18653/v1/2020.acl-main.136
Bibkey:
Cite (ACL):
Zhepei Wei, Jianlin Su, Yue Wang, Yuan Tian, and Yi Chang. 2020. A Novel Cascade Binary Tagging Framework for Relational Triple Extraction. In Proceedings of the 58th Annual Meeting of the Association for Computational Linguistics, pages 1476–1488, Online. Association for Computational Linguistics.
Cite (Informal):
A Novel Cascade Binary Tagging Framework for Relational Triple Extraction (Wei et al., ACL 2020)
Copy Citation:
PDF:
https://aclanthology.org/2020.acl-main.136.pdf
Video:
 http://slideslive.com/38928881
Code
 weizhepei/CasRel +  additional community code
Data
NYT10-HRLNYT11-HRLWebNLG