Mixed-initiative natural language dialogue with variable communicative modes

As speech and natural language processing technology advance, it now reaches a stage where the dialogue control or initiative can be studied to realise usable and friendly human computer interface programs such as computer dialogue systems. One of the major problems concerning dialogue initiative is who should take the dialogue initiative when. This thesis tackles this dialogue initiative problem using the following approaches: Human dialogue data is examined for their local dialogue structures; A dialogue manager is proposed and implemented, which handles variations of human dialogue data concerning the dialogue initiative, and experimental results are obtained by having the implemented dialogue managers working with a parser and a generator exchange natural language messages with each other; and A mathematical model is constructed and used to analyse who should take the dialogue initiative when. The rst study shows that human dialogue data varies concerning the number of utterance units in a turn and utterance types independently of the di erence of the dialogue initiative. The second study shows that the dialogues in which the dialogue initiative constantly alters (mixed-initiative dialogues) are not always more e cient than those in which the dialogue initiative does not change (nonmixed-initiative dialogues). The third study concludes that under the assumption that both speakers solve a problem under similar situations, mixed-initiative dialogues are more e cient than non-mixed-initiative dialogues when initiating