The Smart Personal Assistant (SPA) enables users to access e-mail and calendar information using natural language dialogue through a PDA platform. The user interface to the SPA must present the system as a single unified set of backend task assistants, enabling the user to conduct a dialogue in which it is easy to switch between these domains. The SPA is implemented using an agent platform and includes a special BDI Coordinator agent with plans both for coordinating the actions of the task assistants and for encoding the system’s dialogue model. The agent-based dialogue model is at a high abstraction, enabling the domain-independent plans in the dialogue model to be reused in different SPA systems.