System Dynamics: Modelling and Simulation

Abstract

If you don't know where you are going, don't be surprised to end up somewhere else Stuart Burge All systems seek to achieve a purpose. Whether human made or natural, all systems strive to do something. When creating a new system or modifying an existing one, it is done in order that the resultant system does something " useful " . The reason useful is in quotation marks is that " usefulness " of a system depends upon the viewpoint of the observer. The purpose of a system is a property of the whole and not in any of the components. Notice here that there is a close link between emergence and purpose. At this point it is useful to talk about two types of system; designed systems and evolved systems. Designed systems have a defined start and finish to its life. They are human developed systems that have come about by a deliberate conscious act; we put effort into ensuring that the actual emergent behaviour matches the purpose. Designed systems tend to be product-based systems that include, pens, houses, aircraft, etc. It is also possible to include some service-based systems in the designed category and is where the next great revolution in system design will take place. Evolved systems may have specific start and certainly have no end date. They include businesses, institutions, and legislative systems. A classic example of an evolved system is country's tax system. They may even have had a " designed " start, but have been modified in a piecemeal fashion over many years. Evolved systems are potentially immortal but many do die. The use of the term evolved is quite fitting, as their persistence is often a matter of the survival of the fittest. Quite often with evolved systems the actual emergent behaviour doesn't match the stated purpose. And, indeed, one of the reasons evolved systems continue to evolve is because their actual behaviour doesn't match the desired and are therefore constantly subject to change. The fact that this change is often " not thought through " , root causes not found, solutions not explored and implementations rushed can only, as you will see later, cause more problems.