This article proposes a model and rules dealing with the management of the interaction between system design processes and project planning ones. An industrial benchmark analysis has reinforced our belief that the interaction between the two processes has to be supported by models, processes and relevant tools. Firstly, after presenting the results of the analysis, the different entities are defined and the one-to-one relationship or bijection between the structure of the system and the

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... e of the project is made. Then, a model, taking into account design activities and planning activities as well as management of interactions, is proposed in compliance with existing project and design standards. A process of interaction is presented to carry out design and project management. Two interaction modes have been proposed. On the one hand, the structural interaction establishes links between entities of the two domains. On the other hand, the behavioral interaction (subject of this paper) is based on the definition of states for each entity following feasibility and verification criteria, and can thus manage the changes between states. Some rules are defined (precedence and synchronous rules) to forbid certain changes when they are inconsistent and to synchronize them. the design of a system and the building of its design project are crucial and have to be formalized and monitored in order to avoid inconsistencies between these two processes. Recent project failures (A380 Program, Olkiluoto Nuclear Power Plant) have highlighted the fact that the management of system design, project planning and their interactions, is critical. Much interdisciplinary and concurrent work as well as better communication between the design side and the project side are therefore required ([21] and [33]). Co-operation and interactions across engineering teams and project managers are vital to the planning process and the success of the project in terms of quality, delay and cost ([7] and [43]). This statement is true whatever the complexity of the designed system and the stage of its development.