A system is a network which can perform-- or, is expected to perform-- one or more specific processes within specific conditions.
System is an extremely generic concept which applies to all organisms, collectives and machines as well as many other forms and resources. (In fact, most of these forms contain multiple hierarchical levels with systems within systems.) All sciences and technical practices have developed systematically by defining, describing and (sometimes) designing systems, their components and (often, for massive systems) frameworks. In fact, we can identify countless systems; therfore, systems theory, thinking and design can only be practical if we put our awareness and efforts where they matter most instead of trying, impossibly, to identify all systems . For example, it’s often extremely practical and important to define biological, ecological, mechanical and electrical systems, etcetera. We need to focus our attention on systems which reliably perform processes within a practical range of “operating conditions” . For example, a human being (organism) can’t function— or survive— at negative 50 degrees or positive 200 degrees temperature, without extraordinary protection, and yet it’s critically important for us to thoroughly explore all the possibilities of human beings, and how those possibilities relate to all of our biological subsystems (organs and cells, etcetera) as well as the social and technical systems which we use.
Systems can be physical, conceptual or social. Systems can emerge or be designed by agents.
Complex systems are developed by functions which relate outputs and inputs, creating positive or negative feedback, which amplifies or attenuates subsequent inputs. Each system is a network which are sufficiently insulated from other forces to create predictable patterns.
Robust systems have well-defined positive and negative feedback systems which create sustainability and security against predictable and likely risks. Resilient systems are robust and are complexly adaptive to diverse inputs.
Some systems may be identified mainly by networks of physical components. For instance, a toaster is a system which has been created by networking physical components which match modular specifications for systemic function(s).
Systems (including subsystems) frequently use inputs from and create outputs to other systems. Systems appear to exist “separately”, and create complexity, because forces interact intermittently according to distance, timing, resistance and barriers. Systems are often separated by specific forms (or forces) of resistance, and by barriers (including selectively permeable membranes.) The processes which occur in (and link) each system can develop either through “natural emergence”, without known decisions by any agents, and they can also develop through effective design which creates or adds to practically functioning systems. Relationships between systems, due to related inputs and outputs, create varying intensities of interdependence between the resources and agents involved in the different systems, to whatever extent they depend upon related resources, regardless of how each system is or isn't governed.