This paper presents experimental results comparing two different designs for a spoken language interface to entail.We compare a mixed-initiative dialogue style, in which users can flexibly control the dialogue, to a systemiuitiative dialogue style, in which the system controls the dialogue.Our results show that even though the mixedinitiative system is more eflicient, as measured by number of turns, or elapsed time to complete a set of email tasks, users prefer the system-initiative interface.We posit that these preferences arise from the fact that the system initiative inter&e is easier to learn and more predictable.

This paper reports experimental results comparing a mixed-initiative to a system-initiative dialog strategy in the context of a personal voice email agent. To independently test the effects of dialog strategy and user expertise, users interact with either the system-initiative or the mixed-initiative agent to perform three successive tasks which are identical for both agents. We report performance comparisons across agent strategies as well as over tasks. This evaluation utilizes and tests the PARADISE evaluation framework, and discusses the performance function derivable from the experimental data.

Creating high-quality multimedia presentations requires much skill, time, and effort.This is particularly true when temporal media, such as speech and animation, are involved.We describe the design and implementation of a knowledge-based system that generates customized temporal multimedia presentations.We provide art overview of the system's architecture, and explain how speech, written text, and graphics are generated and coordinated.Our emphasis is on how temporal media are coordinated by the system through a multi-stage negotiation process.In negotiation, media-specific generation components interact with a novel coordination component that solves temporal constraints provided by the generators.We illustrate our work with a set of examples generated by the system in a testbed application intended to update hospital caregivers on the status of patients who have undergone a cardiac bypass operation.