In the world of IT planning and design, the word "system" is often used to refer to a technical system -- a collection of electronic components that function together. Another use of the word "system," however, refers to the collection of human actions and interactions that create the social and managerial systems within which technical systems operate. These social and managerial systems are often characterized by a high degree of complexity, variability, and uncertainty.

System simulations provide a structured approach to analyzing and understanding how complex social and managerial systems give rise to problem behaviors, as well as what types of solutions might be applicable to those problems.

Ways to describe and understand feedback. System simulations are structured, computer-based, analytic approaches to describe and understand the feedback complexity in social and/or managerial systems. They show, for example, how a policy influences behavior which in turn influences costs. System simulation models are constructed using specialized simulation software that help users understand these complex, often hidden, relationships.

Time plot simulations support to planning. System simulations explicitly model delays in system functioning as well as feedback loops. This can help you predict and plan for the future behavior of a system under a wide variety of circumstances.

Examining complex systems. System simulations help create models of a problem or a solution when the level of social or managerial complexity surrounding a system is high.

Identifying problematic behaviors. Simulations allow you to identify patterns of inter-agency or inter-organizational decision making that are causing or contributing to a problematic or undesirable pattern of behavior.

Understanding how a technical system fits into social and managerial system. System simulations can help your project team understand how a technical system will fit into, and function within, a complex social or managerial system. Often, the simulation can help to identify forces within the social system that will result in a system that doesn't solve the basic problem. This can lead to redesign of the technical system or to a redesign of the business processes that support the managerial system.

Considering causes and possible solutions to problems. Your project is more likely to succeed if you understand the root causes of the problem, and how one or more proposed solutions may (or may not) act over time to solve or reduce it.

Understanding your part. These models will help members of your management team understand how their decisions contribute either to the creation of problem behavior within a system or to the resolution of it.

Expense. System simulations can be expensive and time-consuming to construct. They require specialized expertise and tools to build and analyze.

Mixes hard and soft data. Because system simulation models integrate a diversity of data sources, ranging from hard data about time to softer and more qualitative estimates of human factors, the output of such models can be confusing and hard to interpret.

Requires high involvement of key actors. Usually all of the key actors in a system need to be involved in the construction of a system simulation. Bringing all the key people together for the amount of time that is required to build a system simulation as a group exercise may be logistically impossible or prohibitively expensive.

Because system simulations require assistance from a skilled modeler, and because they are more complicated and expensive than some other analytic processes, it is useful to have some criteria for knowing when such modeling efforts are warranted. Here are some indicators of when the benefits of such an exercise will probably outweigh the costs:

• when complex feedback is involved,
• when actors from different parts of the system don't readily agree on the root cause of the problem(s) or the possible solution,
• when the predicted impacts of a system on organizational performance are uncertain or when serious risks are involved,
• when the costs of making a mistake in implementation are unacceptably high, and
• when the problem is an important one that has attracted the interest of top management.

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Roberts, N., D. Andersen, R. Deal, M. Grant, and W. Shaffer (1983) Introduction to Computer Simulation: A System Dynamics Modeling Approach. Reading MA: Addison-Wesley.

Senge, P. (1990). The Fifth Discipline. New York: Doubleday.

Senge, P. (1990). "Catalyzing Systems Thinking Within Organizations" In Advances in Organization Development, ed. F. Masarik. Norwood NJ: Ablex.

Wolstenholme, E. (1993). Evaluation of Management Information Systems. Chichester; New York: J. Wiley.