A complex system is neither good nor bad. It is just difficult to analyse.

@Ian,

As always you are correct. But, if a system we find difficult to analyse goes out of hand, then? We cannot ignore a complex system. For examples, a robot with artificial intelligence with simulated human mind functioning by chance due to some accident or some mistake on the part of developer/designer develops certain circuity and becomes superior to human and itself develops tools/shields to become independent then what about the question of master and servant? We cannot afford to ignore a complex system whether social, economic, natural or artificial however difficult it may be to analyse and understand. Although, I do not claim that an entity or system may be completely understood because all our understanding is based on reduction as well as abstraction.

It is not good or bad ... the complex systems are simply there! They challenge and enhance our knowledge and intelligence. We have just started the journey to understand and decode the components and their multi-dimensional interactions within the components, systems, intra-systems and inter-systems. Weather, proteins, economy, brain .... are examples of complex systems. So, let's not bother about good or bad ... our work is to increase our understanding with each passing moment!

Having a complex system means that no one will really understand it completely and be able to analyse it thoroughly. This is actually not bad, because it limits the potability of abuse. While simpler systems can be analysed, understood and flaws can be identified and exploited. Of source, this does not mean that a complex system has ho flaws, it does. They are harder to detect, but the thing is, in complex system, you have certain people/departments who are delegated to analyse their "part of the system" and observe it as system on its own and identify and patch it or suggest possible amendments to it. This way more people are engaged in administering the system, but it is easier for them, because they work with a part of the whole and don't have to understand the whole. This ensures that no one can ever be placed in a position to control and/or compromise the whole system, only it's parts.

So, my conclusion would be that complex systems have their disadvantages and advantages and that simple systems have their disadvantages and advantage, but that neither is in its own good or bad as a solution for implementation.

This goes for all systems: political, governing, economical, in informatics, etc.

not only it's not a bad thing, but also it's a category of systems. When there are a huge number of agents which interact with each other in a complicated and unpredctable way, a complex system emerges. Centralized management methods might lead to fail n such systems. So more distributed strategies are needed to develop and utilize.

I forgot to mention one very important thing as well.

Simple systems tend to be more stable in general, but there is a catch. In case of unpredicted external influence they can either evolve to be more stable and efficient or to be put out of order and completely destabilised (to the "point of no return" a.k.a. failure).

Complex systems are more adaptable. They constantly change and evolve and when an external influence is introduced parts might evolve into better sub-systems or "parts", and also they can begin to fail, but since a complex system is (exactly that) a synergy of multiples that are sometimes more independent that other parts, the system as a whole wont always be equally compromised.

This is also in a way good and in a way bad.

In case of a good influence, a simple system will pick up those changes faster, while a complex system will take more time and will be more inert to them.

In case of a bad or destructive influence, a simple system will be quicker to give in and fail, while a complex one will, again, be more inert to that influence and will not fail as a whole, but only parts of it.

Very complex systems sometimes have redundant parts which can pick up work delegated to other parts and in that way prevent the system going into a blockade.

Most of you implies that complex systems as multi-functional and is a merit for m systems , can we consider that a complex system is an aggregation of multiple simple sub-systems

Complex systems usually accomplish multiple things and overall it might all be a part of one greater field which a complex system is meant to achieve. But you are right, it isn't always so. However, it is the best model to observe.

Political systems and systems of governing and administration in a country or a larger city are also good models to observe when comparing different types of systems.

@ Dr. Juneidi,

"can we consider that a complex system is an aggregation of multiple simple sub-systems" theoretically yes, it is quite possible but as for as evidence is concerned it is an emergent property which cannot be examine in terms of subsystem as in information or computing system or in terms of bits.

@ Dr. Firoz Khan,

the issue is how we going to reduce complexity and harness the functions of the sub systems as simple system for each function , this idea is not recalling back functional and modular Engineering paradigm but to evolve Object Oriented Paradigm , of what is currently working on which is called called "Objective Oriented" or " Goal Oriented"

A complex system can be a merit and can be a curse, can be good and can be bad. Fundamentally a system is complex, if its behavior cannot be easily described. One way this can arise is if the system consists of many components, with numerous relationships and interactions between these components.

Complexity is a function of two fundamental characteristics of a system:

1) Structure, This reflects the way information flows within the system and

2) Amount of uncertainty within a given system, or its "degree of fuzziness".

So, you can make a system more complex by adding more structure, this is in general a good thing to do. But you can also make a system more complex by making it more fuzzy, more uncertain. This is in general not a good thing to do.

Let me give you an example: If your business is getting more complex because it is growing (adding structure) then you are probably doing okay. But if your business is becoming more complex but is not growing ( in structure, for example) then you will soon be in trouble.

Salaheddin, I don't think you can think of a complex system as simply an aggregate of subsystems, that would be a complicated system like a car. Complex systems require both characteristics of emergent behaviours and self organisation. This CSIRO Ste provides good resources http://www.csiro.au/Organisation-Structure/Divisions/Marine--Atmospheric-Research/Complex-systems-science-2/About-Complex-Systems.aspx including re agent based modelling, etc.

Complex systems are very good because they allow resilience and evolution as on Earth. But they are difficult to predict and control eg in healthcare which is resilient to the improvement interventions we try, because the systems can then result in unpredictable unintended consequences distant in time and place that may be worse overall or require separate forms of control....

Susan, do not mix between complex and complicated systems .This discussion redirected into Complex VS. Complicated system , maybe complex systems are " an aggregation of simple sub-systems" , Complicated system is "Overlapped and and inter-functional sub-system" . let's debate on this.

Whether Complex System is good or bad depends on the context. However, typically a complex system with positive connotation is built to address a complex issue and at the same time calls for rigorous testing as well. A simple or non-complex system will not require an in-depth testing either. Whenever we try to solve several issues simultaneously leads to producing a complex system. Therefore, in my opinion, complex system is a solution to the complex requirement and thus not a bad entity at all.

My Question??? Do we have a universal definition of complex system? If we can have one, we may have a good answer to the original question.

Furthermore viewing complex system as "an aggregation of simple sub-systems" theoretically true but in my humble opinion it’s a simplistic view – an old idea Divide-and-Conquer. What we all know is that complex systems generally behave in unexpected ways that can’t easily predictable from the behavior of their components (can I say sub-systems?); a.k.a. emergent behavior.

And finaly allow me to say, to me its a curse.

Traditional Divide-and-Conquer approachs can't be considered as complex systems. Because there is no interaction between sub-systems in such approachs. But if we define a framework for sub-systems to interact, an initial formal definition for complex systems will be reached. When sub-systems gain the ability to interact and communicate autonomously and without the need for a central coordinator, unexpected and complicated patterns will emerge. Like swarm intelligence paeadigms, cellular automata and etc....

In fact, the most significant point is having the ability to learn and adapt to a changing environment.

Bahram, Just to be clear here, I am not saying that traditional Divide-and-Conquer can be considered a complex system. What I mean is, approaching complex system as "an aggregation of simple sub-systems" is simplistic view and if this is true, Divide-and-Conquer solutions will solve the complexity problem.

Sameer, why you think that complex system is "unpredictable in behavior " ,on this assumption modern IT life style is unpredictable which is not on the contrary it's more precise