A decision model in decision theory is the starting point for a decision method within a formal (axiomatic) system. Decision models contain at least one action axiom.

An action is in the form "IF <this> is true, THEN do <that>". An action axiom tests a condition (antecedent) and, if the condition has been met, then (consequent) it suggests (mandates) an action: from knowledge to action. A decision model may also be a network of connected decisions, information and knowledge that represents a decision-making approach that can be used repeatedly (such as one developed using the Decision Model and Notation standard).

Excepting very simple situations, successful action axioms are used in an iterative manner. For example, for decision analysis, the sole action axiom occurs in the Evaluation stage of a four-step cycle: Formulate, Evaluate, Interpret/Appraise, Refine. Decision models are used both to model a decision being made once, as well as to model a repeatable decision-making approach that will be used over and over again.