HIERARCHICAL BELIEF STATES FOR DIGITAL ASSISTANTS

Systems and processes for operating a digital assistant using a hierarchical belief state are disclosed. In an example process, a user utterance of a dialogue is received. A belief state for the dialogue is determined. The belief state comprises a plurality of dialogue slots. Each dialogue slot of the plurality of dialogue slots includes a respective marginal certainty for a concept or property represented by the respective dialogue slot. A first dialogue slot of the plurality of dialogue slots further includes one or more joint certainties for one or more interpretations arising from the first dialogue slot. Based on the marginal certainty of each dialogue slot of the plurality of dialogue slots and the one or more joint certainties of the first dialogue slot, a policy action is selected from a plurality of candidate policy actions that correspond to the belief state. The selected policy action is performed.