Feedback – the process of comparing system output with input to modify subsequent output.
Formal model – an explicit (objective) representation of a system, as opposed to a purely mental (subjective) conceptualization. Formal models can be categorized as descriptive, predictive or prescriptive (also called normative).
Formalization – act of giving definite form to a concept by means of symbols.
Function – (1) a characteristic action or behavior that distinguishes a given entity. (2) a relation which uniquely associates members of one set with members of another set.
