This paper considers measures of the complexity of human-computer spoken dialogues, and describes how these measures can be applied in dialogue engineering for automated telephone services. The paper highlights fundamental concepts involved in measuring the complexity of spoken telephone dialogues and develops a design evaluation approach based on a set of measures of dialogue complexity at a hierarchy of linguistic levels, focusing on measures of information in spoken dialogues. The measures described are applied to dialogues which have been engineered for use in automated telephone services for catalogue ordering and credit card payment. Aspects of the dialogue component of this telephone speech interface are described and measures of information complexity are used to evaluate the dialogues for alternative designs of spoken user interfaces. The results of the analysis are presented in detail.
Keywords: spoken dialogues, dialogue engineering, automated telephone service, complexity measures