Dialogue modelling attempts to 
determine the way in which a dialog is 
developed. The dialogue strategy (i.e.,
the system behaviour) of an automatic
dialogue system is determined by the 
dialogue model. Most dialogue systems 
use rule-based dialogue strategies, 
but recently, the probabilistic models 
have become very promising. We present 
probabilistic models based on the 
dialogue act concept, which uses user 
turns, dialogue history and semantic 
information. These models are 
evaluated as dialogue act labelers. 
The evaluation is carried out on a 
railway information task.