  With the rapid explosion of the World Wide Web, it is becoming increasingly
possible to easily acquire a wide variety of information such as flight
schedules, yellow pages, used car prices, current stock prices, entertainment
event schedules, account balances, etc. It would be very useful to have spoken
dialogue interfaces for such information access tasks. We identify portability,
usability, robustness, and extensibility as the four primary design objectives
for such systems. In other words, the objective is to develop a PURE (Portable,
Usable, Robust, Extensible) system. A two-layered dialogue architecture for
spoken dialogue systems is presented where the upper layer is
domain-independent and the lower layer is domain-specific. We are implementing
this architecture in a mixed-initiative system that accesses flight
arrival/departure information from the World Wide Web.
