Are We A System Or A Network? A Hat Tip to Russell Ackoff, Again

Almost everything these days is a network (5B Google hits). Or a system (10B Google hits). Are systems and networks the same thing? Are they very different?

A very brief side trip into definitions and etymology might answer this for us, definitively. Network is defined by OED as “a group or system of interconnected people or things.” Network comes from the Proto-Germanic *natjo, perhaps originally “something knotted,” from PIE root *ned– “to bind, tie” and *werka– “work,” from PIE *werg– “to do.” So, from the Proto-Germanic for bound-together work or interconnected people or things. System is defined by OED as “a set of things working together as parts of a mechanism or an interconnecting network; a complex whole.”  System comes from the Greek systema “organized whole, a whole compounded of parts,” from syn– “together,” from PIE root *sta– “to stand, make or be firm.” So, from the Greek for interconnected parts. OED seems to partially define a network as a system and a network as a system. So, the definitions and etymology do not seem to clarify much.

Then, there is Russell Ackoff. For me it is always worth it to go back to Russell Ackoff, especially for clarity around seemingly complex themes. In his 2010 book Differences That Make a Difference: An Annotated Glossary of Distinctions Important in Management, Ackoff distinguishes networks from systems, clarifying their distinct power and purpose.

A system is a whole that is defined by its function in a larger system of which it is a part. (An automobile, for example, is defined for its role in the transportation system: a university by its role in the educational system.) It has at least two essential parts–parts without which it could not perform its defining function. For example, an automobile cannot function without a motor, fuel, pump, or battery. A person cannot function without a brain, lungs, and a heart. The essential parts have five essential characteristics: (1) Each can affect the behavior or properties of the whole; (2) The way an essential part affects the whole depends on what at least one other part is doing. The effects of the parts are interdependent; (3) Every two essential parts are connected, directly or indirectly; (4) Subsets of essential parts (subsystems) also can affect the properties or behavior of the whole, and the way they affect the whole depends on at least one other subsystem; (5) There is a direct or indirect connection between every pair of subsystems. It follows that a system is a whole that cannot be divided into independent parts. Its properties and behavior derive from the interactions of its parts, not their actions considered separately.

A network is a whole whose function is to enable communication between its parts. In a well-designed network, there is a connection between every possible pair of parts. But in a network, unlike a system, there are no essential parts. If any part is removed, there are alternative ways to connect the parts affected.

The parts of a system many form a network, but not every network is a system. The so-called “telephone system” is not a system but a network. It has no essential parts. However, a telephone company is a system. If a collection of parts is neither a system nor a network, it is an aggregation, like a crowd or inventory of parts. For example, consider the wired telephone network. If the connection between Philadelphia and New York is broken, one can still reach New York from Philadelphia by going through any number of cities: for example, Trenton, New Brunswick, and Newark. But, if an essential part of a system–for example, the motor from an automobile–is broken the automobile cannot perform its function.

Ackoff, R. L. (2010). Differences That Make a Difference: An Annotated Glossary of Distinctions Important in Management. Devon, UK, Triarchy Press, pp. 119-120.

Thank you, once again, Russell Ackoff for this clarity. A system is a set of interrelated parts, where the contribution of each is essential to the purpose and behavior of the whole. A network is a set of interrelated parts, providing robust communication among its parts. An aggregation is a pile of parts. Clear. So, are you a system, a network, or an aggregation?