Posts Tagged ‘Systems of Systems’


When are Systems Of Systems not Systems?

November 26, 2010

Only the most trivial of systems are not composed of other systems, yet the term ‘System of Systems’ is used as if describing something distinct. So what is it? What’s the difference between a ‘system of systems’ and a ‘system of … things that aren’t systems’?

Is it a bigger thing?

For example, this paper (Net-Centric, Enterprise-Wide System-of-Systems Engineering And The Global Information Grid PDF) argues that systems-of-systems are not just a scaling up of systems-of-components but are distinguishable as follows (click to enlarge):

Yet plainly many of these are simply differences of scale:

Local vs global is a simple geographic scaling, and is not really valid, depending on how you define ‘global’.

Similarly lifespan extents are in practice in the eye of the beholder. Complex systems of systems such as human beings have lifespans of decades, yet systems of humans such as enterprises have typically similar lifespans.

Similarly (not) understanding information flows is a feature of the engineer not the component; a transport company is a system of components that include vehicles. Vehicles are systems of components that include engine management systems, that in turn include microchip information exchanges that are often not very well understood at all when operating in the real world, and so on. Understanding of the information exchanges varies from engineer to engineer and community to community.

The required functions too change; even if a car has been ‘optimised’ for a certain set of requirements, the uses that the owner might want to put it to changes from journey to journey and during the lifetime of ownership as the owner’s lifestyle changes.

And so on.

Is it a new thing?

This paper (A New Accident Model for Engineering Safer Systems PDF), was included as a discussion paper at a Systems of Systems Architecture (Safety) group and claims that we are dealing with new and more complicated systems as technology enables more complex systems.

Yet biological systems are some of the most complex systems that we encounter, and the primitive farmer has had to run systems of these components as a matter of course. The horse pulling a plough, for example, has to be managed as a system and yet is an essential component of some subsistance agricultural farms.

Reverse the polarity…

A system of components is supposedly ‘well understood’ and so there is a top-down view of how the components interrelate and the components are seen as discrete black boxes. It is easy to diagram and describe.

With systems of systems these components are opened up and the interrelationships are less well understood; a kind of ‘inside out’ view, where we sit within this large surrounding system, looking around at a complexity we can’t comprehend.

These are descriptions of viewpoints and the engineers’ understanding though, not descriptions of the systems themselves. As long as the terms are used as a way to categorise viewpoints then this is alright, but unfortunately the terms seem to be used to describe a ‘new’ problem, and so therefore we need ‘new’ ways of approaching it, thus discarding much of what we have learned about systems engineering.

It’s a learning thing

It may be that this is simply part of the way that we preserve corporate or community knowledge. Because expertise is hard to pass on, there is a tendency as new blood arrives to generate ‘new paradigms’ that are a small iterative improvement (hopefully) on the previous paradigm. People are essentially re-learning many existing concepts under the guise of exciting shiny new terms that provide the motivation. More later…

It’s just that I don’t understand

As long as we don’t lose sight of the fact that systems of systems are ‘just’ systems, the term can be use to indicate the engineers’ perhaps quite legitimate incomprehension of the complexity of the system under discussion.