This paper describes TOBI, a system that interacts with the user in
natural language and can treat temporal relations and counterfactual
utterances. This system presents three peculiar
characteristics. First, it tackles the classical problem of temporal
presuppositions from a novel and general point of view; second, the
system draws a clear distinction between two types of knowledge namely
ontology and content; third, the system is not based on a classical
deductive system, but it uses the more primitive and flexible notion
of model-based evaluation.