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A system is an abstraction used to explain organization. As such, system is a perspective of organization that seeks to explain that organization. A particular organization -- with its characteristics, behaviors, and functions -- may or may not fit a system perspective. Complexity science offers alternative perspectives of organization than those of systems science. It is what Kant calls a regulative idea, not a constitutive idea.

A system is an entity that maintains its existence and functions as a whole through the interaction of its parts. The behavior of the system emerges from the interactions of the parts rather than the parts themselves.

Nature of a system (Ackoff, 1999, pp 5-9) --
A system is a set of two or more elements that satisfies the following three conditions:

  • The whole has one or more defining properties or functions.
  • Each part of the set can affect the behavior or properties of the whole.
  • There is a subset of parts that is sufficient in one or more environments for carrying out the defining function of he whole; each of these parts is necessary but insufficient for carrying out this defining function.
  • The way that each essential part of a system affects its behavior of properties depends on (the behavior or properties of) at least one other essential part of the system.
  • The effect of any subset of essential parts on the system as a whole depends on the behavior of at least one other such subset.

Every part of a system has properties that it loses when separated from the system, and every system has some properties - its essential ones - that none of its parts do.

Environment of a system (Ackoff, 1972, pp 19) --
A set of elements and their relevant properties, which elements are not part of the system, but a change in any of which can cause or produce a change in the state of the system. A system's environment, then, consists of all variables that can affect its state. External elements that affect irrelevant properties of a system are not part of its environment.

System boundary and environment (Gharajedaghi, 2006, pp 153-154) --
""...the systems boundary is a subjective construct defined by the interest and level of influence and/or authority of the participating actors. The system, therefore, consists of all variables that could be sufficiently influenced by the participating actors."" ""...the environment in which the system must remain viable consists of all those variables that, although affecting the system's behavior, could not be directly influenced or controlled by the participating designers.""

Other ways of describing a system --
The properties of the system are the properties of the whole, not the properties of the parts. The properties of the whole emerge from the unique combination of parts. The more complex the system, the more unpredictable the properties of the whole are.

Systems are both composed of systems, referred to as sub-systems, and make up portions of larger systems.

All parts of a system are connected directly or indirectly. The influence of one part to another ultimately feeds back to the part originating the influence. This circular activity is described as a feedback loop.

Universal system --
Ultimately, there is only one system - the universe. All other ""systems"" are thus subsystems of the universe. For obvious reasons of practicality, the scope of phenomena examined must be reduced, otherwise their complexity would be overwhelming and of little value. Therefore, boundaries are drawn around phenomena to capture what we feel is relevant to our particular needs at the time.. What is outside the boundary is called the environment and what is inside the boundary is called the system. That is why our pragmatic definitionsnew of systems include the boundary and environment as essential elements of the definition of a system.

Management considerations --

  • Systems cannot be understood with analytical techniques, synthesis, i.e. systems thinking, is required.
  • Systems are notoriously difficult to change, unless the leverage points for change are understood.
  • Systems are only as strong as their weakest link.