@InProceedings{takeno-nagata-yamamoto:2017:WAT2017,
  author    = {Takeno, Shunsuke  and  Nagata, Masaaki  and  Yamamoto, Kazuhide},
  title     = {Controlling Target Features in Neural Machine Translation via Prefix Constraints},
  booktitle = {Proceedings of the 4th Workshop on Asian Translation (WAT2017)},
  month     = {November},
  year      = {2017},
  address   = {Taipei, Taiwan},
  publisher = {Asian Federation of Natural Language Processing},
  pages     = {55--63},
  abstract  = {We propose {\em prefix constraints}, a novel method to enforce
	  constraints on target sentences in neural machine translation. It
	  places a sequence of special tokens at the beginning of target
	  sentence (target prefix), while side constraints
	  \cite{sennrich2016controlling} places a special token at the end of
	  source sentence (source suffix). Prefix constraints can be predicted
	  from source sentence jointly with target sentence, while side
	  constraints must be provided by the user or predicted by some other
	  methods. In both methods, special tokens are designed to encode
	  arbitrary features on target-side or metatextual information. We
	  show that prefix constraints are more flexible than side constraints
	  and can be used to control the behavior of neural machine
	  translation, in terms of output length, bidirectional decoding,
	  domain adaptation, and unaligned target word generation.},
  url       = {http://www.aclweb.org/anthology/W17-5702}
}