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A layman explanation of Viable System Model (#vsm #systemsthinking #stwg)

October 13th, 2011 Posted in Systems Thinking Tags: ,

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VSM Model

VSM Model

I often talk on this blog about the VSM (not to be confused with Lean’s Value Stream Maps). Here’s my try at laying down a quick introduction to it.

First of all, the reader should open the picture on the right in a new window. I’ll refer to it.

The VSM is a model created by Stafford Beer that describes what ought to be done for an organization to be viable (i.e. to sustain itself over time). There are three kind of components in it:

  • Environment (left oval on the diagram), obviously out of the System, defined as Operations+Management
  • Operations (circles in the middle)
  • Management (squares and triangles on the right)

The VSM is an embodiment of Ross Ashby’s law of requisite variety. What does it mean?

Variety is loosely defined as “the number of different states a system can be in”.

The Law of Requisite Variety states that for a system to effectively control another one, it must feature at least as much variety as the one it wants to control.

So these are the basis of the VSM. Here is how it goes.


The Environment is what the system wants to control, so the system must bear the requisite variety, either genuinely or through attenuation (which means that different states of the Environment are managed through the same response from the System because, from the point of view of the System, they fall into the same “category”).

So, in front of each part of the Environment the System wishes to control, there a corresponding Operations part that interacts with it.


Operations manage parts of the Environment. As these parts may overlap, different Operations sub-systems need to communicate (represented as the big zig zag line between the two circles on the diagram).

Please note an important point:  the VSM is a recursive model, meaning that every Operations is supposed to be a VSM in itself.

The preceding sentence means that each Operation sub-system is autonomous in the management of its portion of the Environment. More on this later.

Yet, as I said above, some parts of the Environment may overlap, meaning that different Operations sub-systems have to cooperate. Which might, sometime, require some external help in the form of Management.

In the VSM, Operations is named “System 1”.


The Management sub-systems are Systems 2, 3, 3*, 4 and 5 with the following roles:

  • System 2 is in charge of all the signaling between Operations and System 3
  • System 3 manages the relations between different Operations sub-systems and resolve any residual conflicts that may not have been resolved between the System 1 themselves . In VSM speech, it’s said to absorb any residual variety not managed by Operations
  • System 3* (three-star) is an audit system onto Operations
  • System 4 is the foreseeing sub-system in charge of anticipating the future of the Environment as a whole to ensure the VSM will evolve accordingly. Operations are mainly in charge of the present of the Environment parts they’re dealing with and of the Future of their part (since VSM being recursive they have their own sub-system 4)
  • lastly, system 5 is the ethos of the whole VSM, the policy, what defines the strategy of the whole.

Usage of VSM

How do you use the VSM? Mainly, there are two possible usages:

  • one is to define the structure of an organization, the VSM being a template against which a real organization may be designed.
  • the other possible usage is as an audit model where an existing organization is assessed against the model to see where some sub-systems could be lacking, possibly impeding viability of the whole, or where parts of the organization may not fit the VSM in which case these parts can be candidates for removal.

On a more pragmatic level, the overall structure of VSM (and Stafford Beer work on that topic) shows that a viable organization is one where operational entities are autonomous with respect to what they have to manage in the environment, yet following an overall strategy defined at global System 5 level.

Communications between Operations need to exist to ensure coordination and someone must be in charge of coordinating the whole (System 3). Time is taken into account by keeping an eye on the future (System 4) and informing the strategy and/or the management of Operations (System 3) where deemed necessary.

The other side of the coin showed by VSM is that any central authority trying to control everything from the top to down is doomed to fail because it will violate the law of requisite variety (it can’t have the requisite variety). The Environment won’t be properly matched by the variety of the system and so the overall viability is at risk.

Finally, I already talked a bit about VSM (by giving my own sources and mindmap) here (the mindmap is about other principles exposed by Stafford Beer).







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