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  A group of elements organized such that each one is in some way interdependent (either directly or indirectly) with every other element: in addition, many analysts also require that the system have a function, goal or purpose (if only the maintenance of the system itself), although this does not imply either conscious goals or deliberate intent (cf. teleology), so that systems ideas are akin to those of functionalism. Identification of a system involves delimiting its boundaries, identifying its constituent elements, and defining its function. Some systems may have clear, objective existence (as with a domestic hot-water system or a car engine), but in many geographical studies isolation of a system involves a fairly arbitrary abstraction of a part from a whole in order to facilitate study: unwise abstractions involve studying chaotic conceptions, from which few valid conclusions can be drawn.

Studies of systems have to address four main issues:

{img src=show_image.php?name=2022.gif } Whether the system is open or closed. A closed system has no links to or from a surrounding environment whereas open systems (much more common in geography) have, and interact with their milieux; {img src=show_image.php?name=2022.gif } Whether the system can be divided into subsystems, clusters of interdependent elements which are only weakly-linked to the remainder of the system; {img src=show_image.php?name=2022.gif } Whether the links involve flows, causal relationships or \'black-box\' relationships (in which the consequence of the link is known — i.e. if A in element x then B in element y — but the causal factors are not); and {img src=show_image.php?name=2022.gif } Whether there is feedback in the system, such that change in x may stimulate change in y, and this in turn will have an impact on x, either negative or positive. The interval between a disturbance to a system and the return to an equilibrium state is known as the relaxation time.In geography, the concept of a system is sometimes used relatively loosely to stress the interdependence of phenomena (as in the concept of an ecosystem), but some analysts (especially physical geographers) have used formal systems analysis methods to examine interdependent phenomena. (AMH)

Suggested Reading Bennett, R.J. and Chorley, R.J. 1978: Environmental systems: philosophy, analysis and control. London: Methuen; Chapman, G.P. 1977: Human and environmental systems. London: Academic Press; Huggett, R.J. 1980: Systems analysis in geography. Oxford: Clarendon Press.



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