The system of systems (SoS) is a system whose definition is based on pre-existing independent systems in the runtime environment. The latter is in perpetual evolution thus forcing a recurrent adaptation of the SoS. Thus, during their life cycle the SoS are very exposed to the problem related to the evolution mentioned above. This problem is mainly due to a poor communication between the requirement definition stage and the design stage. In this paper we propose a method for addressing SE for SoS using the concepts Mission and Role. The first one allows the definition of the SoS's behavior, while the second allows to abstract this definition with respect to the constituent systems that may actually exist in the environment. This definition will be translated into an abstract architecture. The later will serve as a guide and controller of the choices proposed by the system architect during the design and evolution stages. With our approach we have correctly defined an SoS concerning crowd management during a sport event.