Learning to Discriminate Noises for Incorporating External Information in Neural Machine Translation

Previous studies show that incorporating external information could improve the translation quality of Neural Machine Translation (NMT) systems. However, these methods will inevitably suffer from the noises in the external information, which may severely reduce the benefit. We argue that there exist two kinds of noise in this external information, i.e. global noise and local noise, which affect the translation of the whole sentence and for some specific words, respectively. To tackle the problem, this study pays special attention to the discrimination of noises during the incorporation. We propose a general framework with two separate word discriminators for the global and local noises, respectively, so that the external information could be better leveraged. Empirical evaluation shows that being trained by the dataset sampled from the original parallel corpus without any extra labeled data or annotation, our model could make better use of external information in different real-world scenarios, language pairs, and neural architectures, leading to significant improvements over the original translation.