This paper proposes a hierarchical attentional neural translation model which
focuses on enhancing source-side hierarchical representations by covering both
local and global semantic information using a bidirectional tree-based encoder.
To maximize the predictive likelihood of target words, a weighted variant of an
attention mechanism is used to balance the attentive information between
lexical and phrase vectors. Using a tree-based rare word encoding, the proposed
model is extended to sub-word level to alleviate the out-of-vocabulary (OOV)
problem. Empirical results reveal that the proposed model significantly
outperforms sequence-to-sequence attention-based and tree-based neural
translation models in English-Chinese translation tasks.

本文提出了一种层次注意机制的神经翻译模型，采用双向树形编码器来增强源端层次表示，用加权变异的注意机制平衡词汇和短语向量之间的信息，通过树形稀有词编码将该模型扩展至亚字级别以缓解词汇缺失的问题，实证结果表明，该模型在英汉翻译任务中显著优于序列到序列的注意力机制和基于树的神经翻译模型。