The initial robot bartender makes use of a rule-based social state recogniser , which infers the users’ social states using guidelines derived from the study of human-human interactions in the bartender domain. The rulebased recogniser has performed well in a user evaluation of the initial, simple scenario . However, as the robot bartender is enhanced to support increasingly complex scenarios, the range of multimodal input sensors will increase, as will the number of social states to recognise, making the rule-based solution less practical.