A Specification Technique for Building Interface Agents in a Web Environment

This papers explores some system design issues regarding the structuring and information flow of complex distributed virtual environments (VEs) containing one or more users and dialogue agents. A specification technique is proposed for modelling such systems. We define a specification technique as a suite of interrelated specification languages. It is argued that specification techniques should support gradual design refinement. Therefore, the proposed technique provides several detail levels of specification. Furthermore, the technique tries to explicitly address distributed implementation issues right from the start. Even prototypes made using the technique are suited for distributed usage. The basic idea behind the technique is that all physical objects, such as user interface components and objects in the VE, are modelled as separate software components. These are arranged in a specific structure, reflecting the actual physical or conceptual structure of the objects. A change notification model is provided that enables each component to react to events from its local structural environment, including additions and removals of other components. The technique is illustrated by means of a Web-based multi-user VE incorporating an environment-aware dialogue agent. The example shows how such a system may be structured in a natural way using the technique and may be specified concisely. The provided change notification model may be considered effective, as it largely replaces the need to directly pass messages between components. However, the still limited expressivity of the change notification model was sometimes found cumbersome, and needs to be improved.