Phrase-level Active Learning for Neural Machine Translation

Junjie Hu, Graham Neubig


Abstract
Neural machine translation (NMT) is sensitive to domain shift. In this paper, we address this problem in an active learning setting where we can spend a given budget on translating in-domain data, and gradually fine-tune a pre-trained out-of-domain NMT model on the newly translated data. Existing active learning methods for NMT usually select sentences based on uncertainty scores, but these methods require costly translation of full sentences even when only one or two key phrases within the sentence are informative. To address this limitation, we re-examine previous work from the phrase-based machine translation (PBMT) era that selected not full sentences, but rather individual phrases. However, while incorporating these phrases into PBMT systems was relatively simple, it is less trivial for NMT systems, which need to be trained on full sequences to capture larger structural properties of sentences unique to the new domain. To overcome these hurdles, we propose to select both full sentences and individual phrases from unlabelled data in the new domain for routing to human translators. In a German-English translation task, our active learning approach achieves consistent improvements over uncertainty-based sentence selection methods, improving up to 1.2 BLEU score over strong active learning baselines.
Anthology ID:
2021.wmt-1.117
Volume:
Proceedings of the Sixth Conference on Machine Translation
Month:
November
Year:
2021
Address:
Online
Editors:
Loic Barrault, Ondrej Bojar, Fethi Bougares, Rajen Chatterjee, Marta R. Costa-jussa, Christian Federmann, Mark Fishel, Alexander Fraser, Markus Freitag, Yvette Graham, Roman Grundkiewicz, Paco Guzman, Barry Haddow, Matthias Huck, Antonio Jimeno Yepes, Philipp Koehn, Tom Kocmi, Andre Martins, Makoto Morishita, Christof Monz
Venue:
WMT
SIG:
SIGMT
Publisher:
Association for Computational Linguistics
Note:
Pages:
1087–1099
Language:
URL:
https://aclanthology.org/2021.wmt-1.117
DOI:
Bibkey:
Cite (ACL):
Junjie Hu and Graham Neubig. 2021. Phrase-level Active Learning for Neural Machine Translation. In Proceedings of the Sixth Conference on Machine Translation, pages 1087–1099, Online. Association for Computational Linguistics.
Cite (Informal):
Phrase-level Active Learning for Neural Machine Translation (Hu & Neubig, WMT 2021)
Copy Citation:
PDF:
https://aclanthology.org/2021.wmt-1.117.pdf
Video:
 https://aclanthology.org/2021.wmt-1.117.mp4