Neural belief tracker: data-driven dialogue state tracking using semantically specialised vector spaces
18th May, 2017
Speaker: Nikola Mrkšić,doctoral candidate, University of Cambridge, Cambridge, U.K.
Abstract: One of the core components of modern spoken dialogue systems is the belief tracker, which estimates the user's goal at every step of the dialogue. However, most current approaches have difficulty scaling to larger, more complex dialogue domains. This is due to their dependency on either: a) Spoken Language Understanding models that require large amounts of annotated training data; or b) hand-crafted lexicons for capturing some of the linguistic variation in users' language. We propose a novel Neural Belief Tracking (NBT) framework which overcomes these problems by building on recent advances in representation learning. NBT models reason over pre-trained, semantically specialised word vectors, learning to compose them into distributed representations of user utterances and dialogue context. Our evaluation on two datasets shows that this approach surpasses past limitations, matching the performance of state-of-the-art models which rely on hand-crafted semantic lexicons and outperforming them when such lexicons are not provided. Finally, we will discuss how the properties of underlying vector spaces impact model performance, and how the fact that the proposed model operates purely over word vectors allows immediate deployment of belief tracking models for other languages.