Definitional Rule

1 Definition

A rule that is intended as a definitional criterion.

Notes: Compare to definition. Evaluation of a definitional rule (also called structural rule in SBVR) always classifies or computes something using known facts, shaping what the business knows about itself and the world. Consider the example: A customer must be considered a gold customer if the customer places more than 12 orders during a calendar year. Evaluation of this definitional rule for any given customer indicates whether the customer is or is not gold given known facts. Consider another example: The total price of an order item must be computed as the product unit price times its quantity. Given any order item, evaluation of this definitional rule indicates the one result for total price that the known facts justify.

Although SBVR does not require it, we prefer to treat definitional rules separately from definitions. During day-to-day business activity, definitional rules are used to evaluate 'where you are' - that is, the current state of affairs - as the need arises. The result reached in each evaluation is only as good as the definitional rules themselves. Poor or misapplied definitional rules yield poor or inconsistent results. In that case, some aspect of the know-how 'breaks down' - it simply does not 'work' properly.

Contrast with behavioral rule. Definitional rules and behavioral rules are fundamentally different. Definitional rules are about how the business organizes (i.e., structures) the operational business concepts basic to its know-how. They give shape - i.e., structure - to core operational concepts of the business. In SBVR, definitional rules always carry the sense of necessity or impossibility; behavioral rules always carry the sense of obligation or prohibition. Disregard for behavioral rules leads to violations and possible sanctions; misapplication of definitional rules leads to miscalculations and off-base conclusions - but only indirectly, if at all, to violations.