Systems

system is an assemblage of related elements comprising a whole, such that each element may be seen to be a part of that whole in some sense. That is, each element is seen to be related to other elements of and/or the whole system. It is generally recognized that while any element of a system need not have a (direct) relationship with any other particular element of a system, any element which has no relationship with any other element of a system, cannot be a part of that system.

From the Latin and Greek, the term system meant to combine, to set up, to place together.

A system typically consists of components (or elements) which interface in order to facilitate the 'flow' of information, matter or energy. The term is often used to describe a set of entities which 'act' on each other, and for which a mathematical model or a logical model may be constructed encompassing the elements and their allowed actions.

A system may be a set of rules for governing behavior or organisation. Laws are a system which governs human social behavior. Grammar is a system which governs language usage (in this case, the grammatical elements are the system elements). Cladistics is a system for classifying evolutionary relationships among living things based on derived similarity.

A system may be said to be any assemblage which accepts an input, processes it, and produces an output.

A sub-system is a system which is a proper subset of another system.

Background
At arbritary boundaries, a collection of interrelated components (or, subsystems) may be declared a system and may further be abstracted to be declared a component of a larger system. Systems enable "activities" to be performed. (It is tempting to say that systems enable "things" to be done&mdash; but that is confusing in this context). An engineering example of a system is often a circuit or a physical series (but such a system does not have to physically exist).

Depending on the type of system, a system can often be distinguished from individual (simple) machines, elements or processes of that system by the number, arrangements and complexity of those elements. For example, a pulley is a machine, but an elevator, which incorporates pulleys (amongst other components), is a system. Going to the doctor is a process, but health care is a system.

In the natural world, one would declare that there are systems. For example, the solar system of nine planets orbiting the sun. Isaac Newton's Principia Mathematica Philosophiae Naturalis Book 3 is De mundi systemate (On the system of the world). In the human body, such systems are referred to as the nervous system, the circulatory system, the digestive system, the reproductive system, and the respiratory system. The entire body is also referred to as a system in terms of physiology.

In addition, all so-called "things"— namely objects— are actually systems. For example, a cup is an object, but it is also a system for holding hot or cold liquid, or other material. The cup has a certain shape and a handle, it is made of non-porous material and so on, and it is put together in such a way as to provide a useful function. Describing this thing makes up information, and defines a system. It might be supposed that there can be an infinite regression or progression of such systems, but in a finite world, all things come to an end (perhaps at the level of quarks, leptons, and photons at one end and the Universe at the other).

A number of material points considered simultaneously is called a system of material points, or briefly a system, if some common principle may be said to govern the collection. (H.Hertz 1956, p. 46, §6)

Types of systems
Open systems can be influenced by events outside the declared boundaries of a system. A closed system is self-contained: outside events can have no influence upon the system. In practice many things are a mixture of the two. For example a prison is a closed system because the prisoners can't get out, and the wardens spend most of their time at the prison. However it is also an open system, because it depends on outside factors and the prisoners and wardens do go outside. Dynamic systems have components or flows or both, that change over time.

Physical systems are systems of matter and energy. Conceptual systems are made up of ideas. Conceptual systems generally exist to aid in the accomplishment of specific goals or may be used to model physical systems.

Living systems can refer to parts of a living organism, members of a group of organisms, or groups of organisms that interact with other groups of organisms. Living systems interact with inanimate elements of its environment.

Human systems are people that attempt to accomplish goals together. Human systems may be comprised of smaller groups or sub-systems that may strive to accomplish their own goals at the expense of other living systems or other human systems.

Thermodynamic systems may be: open, closed, and isolated. See system (thermodynamics).

A university system is set of multiple affiliated university campuses, typically sharing a common component of their names, that are geographically distributed, such as multiple state-funded public university campuses throughout a state in the USA.

Systems in information and computer science
In computer science and information science, system could also be a method or an algorithm. Again, an example will illustrate: There are systems of counting, as with Roman numerals, and various systems for filing papers, or catalogues, and various library systems, of which the Dewey Decimal System is an example. This still fits with the definition of components which are connected together (in this case in order to facilitate the flow of information).

System can also be used referring to a framework, be it software or hardware, designed to allow software to run, see platform.

Systems in operations research and management science
In operations research and organizational development (OD), organizations are viewed as human systems (conceptual systems) of interacting components such as sub-systems, processes and organizational structures. Organizational development theorist Peter Senge developed the notion of organizations as systems in his book The Fifth Discipline.

Systems thinking is a leadership competency. Some people can think globally while acting locally. Such people consider the potential consequences of their decisions on other parts of larger systems. This is a basis of systemic coaching.

Organizational theorists such as Margaret Wheatley have also described the workings of organizational systems in new contexts, such as quantum physics, chaos theory, and the self-organization of systems.