Revisiting Higher-Order Dependency Parsers

Erick Fonseca, André F. T. Martins


Abstract
Neural encoders have allowed dependency parsers to shift from higher-order structured models to simpler first-order ones, making decoding faster and still achieving better accuracy than non-neural parsers. This has led to a belief that neural encoders can implicitly encode structural constraints, such as siblings and grandparents in a tree. We tested this hypothesis and found that neural parsers may benefit from higher-order features, even when employing a powerful pre-trained encoder, such as BERT. While the gains of higher-order features are small in the presence of a powerful encoder, they are consistent for long-range dependencies and long sentences. In particular, higher-order models are more accurate on full sentence parses and on the exact match of modifier lists, indicating that they deal better with larger, more complex structures.
Anthology ID:
2020.acl-main.776
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:
8795–8800
Language:
URL:
https://aclanthology.org/2020.acl-main.776
DOI:
10.18653/v1/2020.acl-main.776
Bibkey:
Cite (ACL):
Erick Fonseca and André F. T. Martins. 2020. Revisiting Higher-Order Dependency Parsers. In Proceedings of the 58th Annual Meeting of the Association for Computational Linguistics, pages 8795–8800, Online. Association for Computational Linguistics.
Cite (Informal):
Revisiting Higher-Order Dependency Parsers (Fonseca & Martins, ACL 2020)
Copy Citation:
PDF:
https://aclanthology.org/2020.acl-main.776.pdf
Video:
 http://slideslive.com/38929446