1. A dialog system that uses a dialog move tree to manage a conversation between the dialog system and a user, comprising: a dialog manager to associate the conversation with a complex activity; and a plan engine to execute a plan script in connection with the complex activity, the plan script including a set of atomic dialog activities and logic to control a data and sequence flow of the atomic dialog activities, the set of atomic dialog activities being sub-activities of the complex activity, wherein: the dialog move tree forms a structured history of dialog moves performed by the dialog system and the user in the conversation; the dialog manager dynamically adds to the dialog move tree a node for each occurrence of an atomic dialog activity of the set of atomic dialog activities; and the complex activity is specified via a declarative activity specification language that connects the atomic dialog activities with a process.
1. A dialog system that uses a dialog move tree to manage a conversation between the dialog system and a user, comprising: a dialog manager to associate the conversation with a complex activity; and a plan engine to execute a plan script in connection with the complex activity, the plan script including a set of atomic dialog activities and logic to control a data and sequence flow of the atomic dialog activities, the set of atomic dialog activities being sub-activities of the complex activity, wherein: the dialog move tree forms a structured history of dialog moves performed by the dialog system and the user in the conversation; the dialog manager dynamically adds to the dialog move tree a node for each occurrence of an atomic dialog activity of the set of atomic dialog activities; and the complex activity is specified via a declarative activity specification language that connects the atomic dialog activities with a process. 20. The dialog system of claim 1 , wherein the set of atomic dialog activities for which representative nodes are dynamically added to the dialog move tree includes (a) an activity corresponding to a user utterance associated with a previous or new complex activity and (b) an activity corresponding to a speech output by the dialog system according to the plan script.