ABSTRACT
Activity is often associated with the notion of task, which is defined as a goal to be achieved under determined conditions. Activity answers task goals and demands, but it answers them in a non-passive way. An operator receives the task and answers it according to his own purposes which can lead him to redefine the task, its goals and conditions. Operator, task and activity form a triad in which the terms are in a relationship of co-determination. Let one take the simple (?) example of using a video cassette recorder. The user’s task is to obtain a correct recording, with the technical conditions defined by the properties of the instrument and various constraints. The user has a certain level of competence with regard to the instrument, as well as a more or less great desire to succeed alone, etc., which will influence his activity. The activity will expresses itself by observable trials and errors, by comments concerning the task, satisfaction (or annoyance!), etc. All of this cannot be straightforwardly and completely inferred from previous knowledge about the task and the user. Interaction between the three terms can be easily imagined. The situation can be made more complicated by introducing a collective component into the triad, with a person who comes to give advice.
