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Published in:
2020 | OriginalPaper | Chapter
System Dynamics Modeling: Validation for Quality Assurance
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Excerpt
Model/model system
A model is an abstract representation of a concrete (“real”) system. Models can be descriptive or prescriptive (normative). Their functions can be to enable explanation, anticipation, or design. A distinction used in this contribution is between causal and noncausal models, with System Dynamics models being of the former type. The term model system is used to stress the systemic character of a model; this serves to identify it as an organized whole of variables and relationships, on the one hand, and to distinguish it from the real system which is to be modeled, on the other.
Model validity
A model’s property of reflecting adequately the system modeled. Validity is the main feature of model quality. It is a matter of degree, not a dichotomized property.
Model purpose
The goal for which a model is designed or the function it is supposed to fulfill. The model purpose adheres closely to the end-model user or model owner. Model purpose is the criterion for the choice of a model’s boundary and design.
Modeling process
The process involving phases such as problem articulation, boundary selection, development of a dynamic hypothesis, model formulation, model testing, policy formulation, and policy evaluation (Sterman 2000). The modeling process is followed by model use and implementation, i.e., the realization of actions designed or facilitated by the use of the model.
Validation process
Validation is the process by which model validity is enhanced systematically. It consists in gradually building confidence in the usefulness of a model by applying validation tests as outlined in this entry. In principle, validation pervades all phases of the modeling process and, in addition, reaches into the phases of model implementation and use.