Generating accurate terminology is a crucial component for the practicality and reliability of neural machine translation (NMT) systems. To address this, lexically constrained NMT explores various methods to ensure pre-specified words and phrases to appear in the translations. In many cases, however, those methods are evaluated on general domain corpora, where the terms are mostly uni- and bi-grams (>98%). In this paper, we instead tackle a more challenging setup consisting of domain-specific corpora with much longer n-gram and highly specialized terms. To encourage span-level representations in generation, we additionally impose a source-sentence conditioned masked span prediction loss in the decoder and observe improvements on both terminology translation as well as BLEU scores. Experimental results on three domain-specific corpora in two language pairs demonstrate that the proposed training scheme can improve the performance of existing lexically constrained methods that can operate both with or without a term dictionary at test time.

本文提出了一种简单有效的训练策略，通过应用掩蔽跨度预测模型， 实现了对两种语言的三个特定领域语料库在术语级和句子级翻译方面的持续改进，以解决神经机器翻译系统术语翻译的实用性和可靠性问题。

利用源条件掩蔽跨度预测提高词汇约束的神经机器翻译