Systems thinkers use a number of different terms for the three basic concepts in the "system's triad" so that we have a "real system" as opposed to the "conceptual system" which is sometimes also called the "mental model" which is again different from the (real) descriptive or simulation model. In #Kihbernetics we make the distinction between #Machine, #System and #Model unambiguous following the rules specified in the works of #WRAshby and #HRMaturana

Ashby warns us against our first impulse to point at the pendulum and say 'the system is that thing there' because this has a fundamental disadvantage in that "every material object contains no less than an infinity of variables" from which "different observers (with different aims) may reasonably make an infinity of different selections."

Therefore, there must first be given an #observer, and a #system is then defined as "any set of variables selected by that observer from those available on the real ‘machine‘".

#HRMaturana defines a #system, as "a #configuration of #relations that an #observer abstracts in the flow of #interactions and #transformations of a #collection of #elements distinguished in the observers daily living" that is "spontaneously or artificially #conserved" in its #dynamic within some "#domain of concern" of the observer.

So, in Kihbernetics, the triad looks like this: