Lattice-Based Transformer Encoder for Neural Machine Translation

Fengshun Xiao, Jiangtong Li, Hai Zhao, Rui Wang, Kehai Chen


Abstract
Neural machine translation (NMT) takes deterministic sequences for source representations. However, either word-level or subword-level segmentations have multiple choices to split a source sequence with different word segmentors or different subword vocabulary sizes. We hypothesize that the diversity in segmentations may affect the NMT performance. To integrate different segmentations with the state-of-the-art NMT model, Transformer, we propose lattice-based encoders to explore effective word or subword representation in an automatic way during training. We propose two methods: 1) lattice positional encoding and 2) lattice-aware self-attention. These two methods can be used together and show complementary to each other to further improve translation performance. Experiment results show superiorities of lattice-based encoders in word-level and subword-level representations over conventional Transformer encoder.
Anthology ID:
P19-1298
Volume:
Proceedings of the 57th Annual Meeting of the Association for Computational Linguistics
Month:
July
Year:
2019
Address:
Florence, Italy
Editors:
Anna Korhonen, David Traum, Lluís Màrquez
Venue:
ACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
3090–3097
Language:
URL:
https://aclanthology.org/P19-1298
DOI:
10.18653/v1/P19-1298
Bibkey:
Cite (ACL):
Fengshun Xiao, Jiangtong Li, Hai Zhao, Rui Wang, and Kehai Chen. 2019. Lattice-Based Transformer Encoder for Neural Machine Translation. In Proceedings of the 57th Annual Meeting of the Association for Computational Linguistics, pages 3090–3097, Florence, Italy. Association for Computational Linguistics.
Cite (Informal):
Lattice-Based Transformer Encoder for Neural Machine Translation (Xiao et al., ACL 2019)
Copy Citation:
PDF:
https://aclanthology.org/P19-1298.pdf