Federation of Systems (FoS) (glossary)
A system of systems that rates high on three dimensions of autonomy, heterogeneity, and dispersion. Each component system chooses of its own accord to participate in the FOS as it sees fit. It is a “coalition of the willing.” (Krygiel 1999)
Krygiel, A. J. 1999. Behind the Wizard's Curtain: An Integration Environment for a System of Systems. Arlington, VA, USA: C4ISR Cooperative Research Program (CCRP).