Collaboration among independent systems to achieve a common objective, which a system alone could not accomplish by itself, requires dynamic composition of the participant systems, in addition to mechanisms for leading the interaction of the resultant system of systems. Here is proposed to model system of systems using a multi-agent system approach, where agents represent stakeholders of the systems. Systems are described and defined in terms of social norms, particularly obligations. In order to assemble a set of systems to construct a system of systems, a system interface is defined; such interface establishes what obligations can be assigned to a system, as well as what obligations can assign the system to other systems. The modeling methodology is component based, where each system is a component, and the composition of the systems gives place to the emergence of a system of systems.