12. The method of claim 1 , wherein determining a belief state of the user's intent based on the spoken utterance comprises: creating an observed node in the POT for each dialog slot associated with an unobserved node to which the spoken utterance is assigned, each observed node comprising a probability distribution table including probabilities that the intended node value of the unobserved node is correctly and incorrectly identified; and determining a belief state of user intent based on the joint probability of the unobserved node probability distribution tables and the observed node probability distribution tables.
12. The method of claim 1 , wherein determining a belief state of the user's intent based on the spoken utterance comprises: creating an observed node in the POT for each dialog slot associated with an unobserved node to which the spoken utterance is assigned, each observed node comprising a probability distribution table including probabilities that the intended node value of the unobserved node is correctly and incorrectly identified; and determining a belief state of user intent based on the joint probability of the unobserved node probability distribution tables and the observed node probability distribution tables. 13. The method of claim 12 , wherein the spoken utterance is converted into text using automatic speech recognition, and wherein the spoken utterance is assigned to one or more dialog slots by determining a confidence score for each assignment based on the likelihood that the text was correctly assigned to a dialog slot.