We would like to thank the IBM Almaden Intelligence Augmentation Team (Alfredo Alba, Linda Kato, Chris Kau, Joe Terdiman and Steve Welch) for many fruitful discussions, and the anonymous reviewers for their helpful comments.
we use a bi-directional LSTM transducer (Graves, 2012) which outputs a probability distribution over the three possible labels (B, I, and O) per word, taking into account arbitrary length contexts from both past as well as future words.