System engineering is the art and science of creating effective systems, using whole system, whole life principles. - Derek Hitchins

“The term (system-of-systems) is being applied to the creation of new systems by bringing together existing operational systems under a single umbrella and, presumably, creating or adapting links and interactions between the operational systems, which become subsystems of the higher level umbrella system.”

Emergence is not really mysterious, although it may be complex. Emergence is brought about by the interactions between the parts of a system. The galloping horse illusion depends upon the persistence of the human retina/brain combination, for instance. Elemental gases bond in combination by sharing outer electrons, thereby altering the appearance and behavior of the combination. In every case of emergence, the source is interaction between the parts — sometimes, as with the brain, very many parts — so that the phenomenon defies simple explanation.

The world about us can be looked at in a variety of ways. One way is to see the world as made up from many interacting systems: weather, societal, economic, ecological, floral, faunal, tectonic plate, oceanic, and so on. This is very much a connected view of the world: nothing is isolated and totally independent; everything is part of something bigger, and everything comprises many interacting parts — subsystems.