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Effective handling of dialogue state in the hidden information state POMDP-based dialogue manager

Gašić, M and Young, S (2011) Effective handling of dialogue state in the hidden information state POMDP-based dialogue manager. ACM Transactions on Speech and Language Processing, 7. ISSN 1550-4875

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Abstract

Effective dialogue management is critically dependent on the information that is encoded in the dialogue state. In order to deploy reinforcement learning for policy optimization, dialogue must be modeled as a Markov Decision Process. This requires that the dialogue statemust encode all relevent information obtained during the dialogue prior to that state. This can be achieved by combining the user goal, the dialogue history, and the last user action to form the dialogue state. In addition, to gain robustness to input errors, dialogue must be modeled as a Partially Observable Markov Decision Process (POMDP) and hence, a distribution over all possible states must be maintained at every dialogue turn. This poses a potential computational limitation since there can be a very large number of dialogue states. The Hidden Information State model provides a principled way of ensuring tractability in a POMDP-based dialogue model. The key feature of this model is the grouping of user goals into partitions that are dynamically built during the dialogue. In this article, we extend this model further to incorporate the notion of complements. This allows for a more complex user goal to be represented, and it enables an effective pruning technique to be implemented that preserves the overall system performance within a limited computational resource more effectively than existing approaches. © 2011 ACM.

Item Type: Article
Uncontrolled Keywords: Dialogue belief monitoring Dialogue modelling Dialogue state representation POMDP Reinforcement learning Spoken dialogue systems
Subjects: UNSPECIFIED
Divisions: Div F > Machine Intelligence
Depositing User: Cron Job
Date Deposited: 07 Mar 2014 12:12
Last Modified: 22 Dec 2014 01:20
DOI: 10.1145/1966407.1966409