Software architectures have been recognized as the backbone to the success of any software system. In addition, they are responsible to aggregate quality attributes, such as interoperability, dependability, and maintainability, to these systems. In parallel, currently, a new class of complex software systems has emerged, referred as Systems of Systems (SoS), resulting from a number of operationally and managerially independent software systems working together to fulfill a mission that none system alone could provide. Considering their complexity, the development of SoS has demanded special attention to their software architectures. In this scenario, the description of such architectures, i.e., the way that these architectures are represented/documented, becomes quite important as it can improve communication as well as evaluation and maintenance of these architectures. Despite its relevance, there is still no complete panorama about architectural descriptions of SoS. The main contribution of this paper is to present results of a Systematic Literature Review (SLR) on how SoS software architectures have been described. As main result, there are already important contributions in that direction; however, there is a lack of consensus on how better dealing with these descriptions. We conclude this paper with directions on how a consensus could be achieved and which aspects of the SoS architectural descriptions require further investigation.
