National audienceThis paper present a dynamic semantics for dialogue in terms of commitments. this semantics is used to provide a model theoretic treatment of ambiguity and its effects on the evolutions of commitments as a dialogue proceeds. A first semantics ensures common commitments and has a simple logic for which a complete axiomatization is provided. On the other hand, it poses difficulties for the analysis of particular dialogue moves, in particular acknowledgments, and of disputes. A second semantics that addresses these difficultie
