Context: The systems comprising a system of systems (SoS) are independently acquired, operated, and managed. Frequently, the architecture documentation of these existing systems addresses only a standalone perspective and must be augmented to address concerns that arise in the integrated SoS.
Objective: We evaluated an architecture documentation viewpoint to address the concerns of a SoS architect about a constituent system, to support SoS design and analysis involving that constituent system.
Method: We performed an expert review of documentation produced by applying the viewpoint to a system, using the active review method.
Results: The expert panel was able to use a view constructed using the baseline version of the viewpoint to answer questions related to all SoS architect concerns about a constituent system, except for questions concerning the interaction of the constituent system with the platform and network infrastructure.
Conclusions: We found that the expert panel was unable to answer certain questions because the baseline version of the viewpoint had a gap in coverage related to relationship of software units of execution (e.g., processes or services) to computers and networks. The viewpoint was revised to add a Deployment Model to address these concerns and is included in an appendix.