The growing complexity and interconnectivity of modern systems have led to the evolution of Systems-of-Systems (SoS), which integrate independent systems to achieve shared goals. Among SoS subtypes, Systems-of-Information Systems (SoIS) and Cyber-Physical Systems-of-Systems (CPSoS) are gaining attention, yet SoIS remains underexplored in literature. This study examines SoS types in current research, identifying key characteristics that differentiate SoIS from general SoS, particularly their reliance on information systems to enable data-driven interoperability and dynamic coordination. Through a rapid review, we highlight SoIS’s critical role in domains such as smart cities and smart grids, where real-time data exchange and system interoperability are essential. Our findings underscore the need for targeted methodologies to advance SoIS-specific research and provide a foundation for future exploration of this distinct class of SoS.