All systems consist of inputs and outputs, between and among their internal components and with their external environment. Inputs can take the form of data or signals that originate from other elements or the external environment. Outputs can take the form of data and inputs for use by other elements. The movement of data and signals from one element to another is known as flow. Often, data and signals flow to and from other people or functions; they may also go to a final destination in an external environment. Or, they may originate from an object in an external environment. The final destination is often called a sink; the point of origination is called a source. In some cases, an object may be both. An example is a project that provides information to and receives information from a project management office.
Cybernetics is the term used to study the flow of information among objects. The common term used for the actual flow of data and signals to adapt to the environment is called feedback.
A system has two basic kinds of feedback, positive and negative. Positive feedback is the basis for systemic growth. Negative feedback either helps to maintain equilibrium (or stability) or lose equilibrium (or dissipate). On a project, positive feedback might include outstanding schedule performance; negative feedback might be a high defect rate.
A system also often performs cyclically. One common cycle is a system with a behavior that occurs regularly, in a repeating manner; everything seems to operate in equilibrium, or self- sustaining mode. Everything within the system seems to "hum."
Sometimes, however, a system is out of equilibrium because a trigger, or event, upsets a cyclic behavior pattern. A trigger is frequently external, but can be internally generated, and may cause a system to move into disequilibrium, or out of balance, unless it can restore balance, known as homeostasis. When disequilibrium occurs, a system lacks sustainability to resist movement to a lower state of performance, known as entropy. An example of a project in equilibrium is one that follows a consistent pattern of performance, symptomatic of being on schedule and within budget on a regular, predicable basis. An example of a project out of equilibrium is one with a history of very good performance but suddenly deteriorates according to cost and schedule criteria.
The concept of equilibrium can be useful to the project manager. So can the concept of autopoiesis that ties back to the autonomy, or independence, of a system to determine its own response to an environment and adapt structures and configurations that allow it to respond to a changing environment. An example of autopoiesis is the ability of a project to determine the methodologies to change or forego a response to a changing external environment rather than being "forced" to adhere to an inflexible approach.
Maintaining equilibrium is a maintenance state for a system. It reflects the ability to maintain integrity. Sometimes, however, a trigger will cause a system to reach an excited state, resulting in movement towards disequilibrium.
The structure of a system is an important influence on its behavior when responding to conditions. It reflects the order of the elements; that is, how they are configured. The configuration of relationships within a system will determine its characteristics. This configuration is identified through the configuration of the physical components. The idea is that a change in the configuration of a system will result in a change in its behavior, e.g., reordering the processes, functions, and other elements to get the desired behavior. An example in project management is to change the reporting relationships among the stakeholders, e.g., move from a matrix to a task structure, to improve performance.
By changing structure, or configurations, therefore, one can alter the behavior pattern of a system to achieve results. Structure and behavior pattern are seen as closely related . Change the structure and the behavior pattern will change to achieve the desired results.
The idea of changing structure to alter behavior can be a very powerful tool for project managers. This ability to change structure goes beyond altering objects, e.g., tools. It is also applies to changing the relationships among tools, techniques, and team members . By changing the relationships among objects, project managers can dramatically influence the outcome of their projects.
They do not have to change every object or relationship, however. Rather, they can identify key internal and external ones and decide and act accordingly to achieve leverage. For example, project managers can alter working relationships among team members, resequence tasks , and change the reporting relationships with stakeholders. They can also adopt tools or techniques as catalysts to influence performance, e.g., changing teaming relationships to augment performance.
Implementing such changes is obtainable by recognizing that different categories of links or relationships among elements exist and taking advantage of them when necessary. Some links are causal ; others correlative. Some links are additive, e.g., one element adding to the performance of another. Some links are balancing, e.g., an increase in performance of one result corresponds to a decrease in another.
Linkages can be mapped in several ways to reflect the topology of a system. Mathematical models are one way. Another way, which has increased in popularity, is through mapping. One popular approach is loop diagramming, popularized by Peter Senge. It is an effective way to illustrate the feedback loops existing in a system.
Loops are an effective way to illustrate the different behavior patterns that can occur in system. Loops are reflected in the form of curved arrows to show the "flow of influence." One category of loops reinforces each other, augmenting or decreasing behavior. The other fundamental category of loops is balancing, which stabilizes behavior. Both categories of loops have a profound influence on the behavior of a system. Senge identified several behavior patterns that he designated as system archetypes. These include balancing process with delay, limits to growth, shifting the burden , erosion of goals, escalation, tragedy of the common, fixes that fail, and others. 
 Peter M. Senge, The Fifth Discipline , Currency Doubleday, New York, 1990, pp. 378 “390.