Sequence learning, especially using LSTM (Hochreiter and Schmidhuber, 1997;Graves and Schmidhuber, 2005;Graves, 2013), has become a well-established standard in numerous NLP tasks (Zhou and Xu, 2015;Ma and Hovy, 2016;Wang and Chang, 2016).
sequence-to-sequence models (Sutskever et al., 2014) have grown increasingly popular and are used extensively in, e.g., Machine Translation (Cho et al., 2014;Bahdanau et al., 2015), Sentence Representation (Kiros et al., 2015), Syntactic Parsing , Conversation Modeling (Vinyals and Le, 2015), Morphological Inflection (Faruqui et al., 2016) and Text Summarization (Gu et al., 2016).