Goal-oriented dialog systems assist users to complete tasks such as restaurant reservations and flight ticket booking. Deep neural networks have opened up the possibility of end-to-end learning of the entire goal-oriented dialog system directly from data. End-to-end learning enables automatic adaptation of the different parts of the dialog system accounting for how changes in one part affect the others. Since the entire dialog system is learned directly from the data, the design of the dialog system need not make any assumptions about the domain. This makes it possible to build dialog systems for new domains with different training data, without much domain-specific hand-crafting of the dialog system. With deep neural networks which can potentially capture the complexity of human dialog in natural language, learning neural goal-oriented dialog systems end-to-end holds the promise of bringing dialog systems into our everyday lives.
In this thesis, we identify some of the challenges in end-to-end learning of neural goal-oriented dialog systems and propose methods to address them. We look at four challenges:
1) The challenge posed by the presence of a large number of named entities in goal-oriented dialog tasks. We propose a method to build neural embeddings for named entities on the fly and store them in a key-value table with neural embeddings as keys and the actual named entities as values. The proposed method allows for comparison and retrieval, using neural embeddings as well as actual named entities, which leads to significant improvement in performance, especially in the presence of out-of-vocabulary named entities.
2) The challenge of performing supervised learning of goal-oriented dialog systems with multiple valid next utterances. We propose a method to learn to use different parts of the neural network to encode different predictions of the next utterances with learning of one not interfering with the learning of the others. Our experiments show considerable improvement in the generalization performance.
3) The challenge of handling new user behaviors during deployment of a trained dialog system. We propose a method that learns to anticipate failures and efficiently transfers dialogs to human agents in order to make sure the overall task success of the users remains high. Our experiments show that using our proposed method it is possible to achieve very high user task success while minimally using human agents.
4) The challenge of requiring large amounts of training data for each new dialog task of interest. We show that by selectively learning from a related task's data that is already available, we can improve the performance on a new task of interest that has only a limited amount of training data.PHDComputer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/169752/1/rjana_1.pd
