The many ways of facing temporal uncertainty in planning and scheduling

Generating off line a plan of activities before executing it on line is no longer realistic when one expects disturbances from an uncertain environment. Focusing on temporal plans and uncertain temporal constraints, we show that there are three main ways of tackling the issue: the reactive way, the proactive way and the progressive way, which are illustrated through existing models and systems. In realistic applications, one usually needs all of them, requiring a unified model. Such a model are introduced together with the first results of a modular system developed in the ILOG programming environment.