In the framework of man-machine command dialogues, we argue that actions can be refered to by building up, from the user's utterance, a representation of the intended goal, which the system is to achieve. This goal will be considered as a final state, in order to enable a planning process starting from the current state of the application. Following our purpose, we point out some of the key elements which have to be taken into account, such as the temporal dynamics of predicates and their subordination to the objects of the task. We thus tackle some of the tricky questions encountered in current dialogue systems. Keywords : man-machine dialogue, reference to actions, prepositions, aktionsart.