Object-oriented modelling of spoken language dialogue systems

In this paper we show how established object modelling techniques can be used in the creation of spoken dialogue management systems. One of the motivations behind the particular approach adopted here is the observation that, in spoken human-to-human dialogues, certain skillsets and patterns of dialogue evolution are common to many different contexts; other dialogue skills and accompanying real-world knowledge are required only for more specialised transactions within particular business domains. As a starting point for modelling an automated spoken dialogue management system we recommend a use case analysis of the required functionality. The use case analysis encourages the developer to identify generic-specific relationships and interactions between different dialogue management skills. We consider some of the broad philosophies underlying current dialogue management systems and outline practical high-level dialogue behaviour based on mixed-initiative, frame-based processing, combined with a rigorously applied confirmation strategy. On the basis of the use case requirements analysis, we explore a possible design for an object-oriented dialogue management system, indicating the roles and relationships of the various classes that embody the required dialogue functionality, and showing how implemented objects within the system will interact. The manner of this interaction is such as to allow one overall system to process transactions in several business domains. We also indicate some of the advantages of a rule-based implementation: the proposed design is tailored towards such an implementation in Prolog++. An object-oriented development process places high-level, generic dialogue management functionality at the disposal of more specialised ‘expert’ components. Maintainability and extensibility are therefore enhanced: if the developer chooses to refine generic behaviour, it is immediately available to the more specialised components; if new domain-specific expertise is required, it can be added with minimal impact on generic behaviour.