This class comprises assigned and accepted commitments by teams of actors to carry out a kind of activity within the context of an overall architectural project (Oeuvre). An instance of mission is used in order to be able to document the details of the commitment undertaken by a team within a project. The substance of the mission is continued, accepted obligation over time. An instance of this class comes into being upon the assignment of the particular set of tasks to the particular group and its acceptance thereof. The instance of mission ceases to exist when the assigned tasks have been discharged, the overall ouevre cancelled or the willingness of the assigned and accepting group ceases to hold. The existence of an instance of mission potentially implies moral and legal obligations on the part of the group accepting to undertake the assigned mission.