© Loughborough University, 2004 Types of Systems There are a number of ways in which we may define types of systems.

© Loughborough University, 2004 System Property Complexity Simple systems include those such as a chair which integrate several non- moving parts together Complex systems are those such as social systems that are made up of a multitude of parts and relationships Openness A closed system is one in which there is no interaction between the system and its environment. An open system is one in which there are interactions between the system and its environment. Stability The state of some systems demonstrate the property of equilibrium or steady-state. The state of other systems fluctuate rapidly. Such systems are described as dynamic systems. Adaptive/ Non-adaptive Some systems adapt to changes in their environments. Other systems fail to adapt to changes in their environment. Permanence Systems may exist for a substantial period of time. Other systems exist only for a short period of time. Discrete/ Continuous In some systems the changes between system states are discrete, i.e., at defined intervals. In other systems change is continuous throughout some period. Deterministic/ Stochastic In a deterministic system the behaviour of the system is predictable in every detail In a stochastic system behaviour is affected by random inputs

© Loughborough University, 2004 Control Open systems normally adapt to changes in their external environments. –Hence, the discipline of ecology utilises the concept of open systems to explain the adaptations that animals and plants makes to changes in the physical environment. Control is the mechanism that implements adaptation in most systems. Systems generally exhibit some form of control which enables the system to adapt to changes in its environment.

© Loughborough University, 2004 Performance Control is normally exercised in terms of some defined measures of performance. A monitoring subsystem may only work effectively if there are defined levels of performance for the system. Such performance levels will be defined by higher level systems. In terms of a physical system such as a thermostat such a performance measure will be defined in terms of a temperature level. There are three main types of performance measures: efficacy or utility, efficiency and effectiveness.

© Loughborough University, 2004 Efficacy Efficacy (utility) is a measure of the extent to which a system achieves its intended transformation.

© Loughborough University, 2004 Efficiency Efficiency is a measure of the extent to which the system achieves its intended transformation with the minimum use of resources.

© Loughborough University, 2004 Effectiveness A measure of the extent to which the system contributes to the purposes of a higher-level system of which it may be a sub-system.