Reducing Discontinuous to Continuous Parsing with Pointer Network Reordering

Daniel Fernández-González, Carlos Gómez-Rodríguez


Abstract
Discontinuous constituent parsers have always lagged behind continuous approaches in terms of accuracy and speed, as the presence of constituents with discontinuous yield introduces extra complexity to the task. However, a discontinuous tree can be converted into a continuous variant by reordering tokens. Based on that, we propose to reduce discontinuous parsing to a continuous problem, which can then be directly solved by any off-the-shelf continuous parser. To that end, we develop a Pointer Network capable of accurately generating the continuous token arrangement for a given input sentence and define a bijective function to recover the original order. Experiments on the main benchmarks with two continuous parsers prove that our approach is on par in accuracy with purely discontinuous state-of-the-art algorithms, but considerably faster.
Anthology ID:
2021.emnlp-main.825
Volume:
Proceedings of the 2021 Conference on Empirical Methods in Natural Language Processing
Month:
November
Year:
2021
Address:
Online and Punta Cana, Dominican Republic
Editors:
Marie-Francine Moens, Xuanjing Huang, Lucia Specia, Scott Wen-tau Yih
Venue:
EMNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
10570–10578
Language:
URL:
https://aclanthology.org/2021.emnlp-main.825
DOI:
10.18653/v1/2021.emnlp-main.825
Bibkey:
Cite (ACL):
Daniel Fernández-González and Carlos Gómez-Rodríguez. 2021. Reducing Discontinuous to Continuous Parsing with Pointer Network Reordering. In Proceedings of the 2021 Conference on Empirical Methods in Natural Language Processing, pages 10570–10578, Online and Punta Cana, Dominican Republic. Association for Computational Linguistics.
Cite (Informal):
Reducing Discontinuous to Continuous Parsing with Pointer Network Reordering (Fernández-González & Gómez-Rodríguez, EMNLP 2021)
Copy Citation:
PDF:
https://aclanthology.org/2021.emnlp-main.825.pdf
Video:
 https://aclanthology.org/2021.emnlp-main.825.mp4
Code
 danifg/Pointer-Network-Reordering
Data
Penn Treebank