Design organization : there is more to expert knowledge than is dreamed of in the planner's philosophy

Projet PSYCHO ERGOThe organization of actual design activities, even by experts and even in routine tasks, is not appropriately characterized by the retrieval of preexisting plans ; this organization is opportunistic. This position is defended through a discussion of an important number of empirical design studies. A major cause why design activities are thus organized is that, even if expert designers possess plans which they may retrieve and use, they very often deviate from these plans in order for their activity to satisfy action-management constraints, the most important being cognitive economy