A business rule is a directive that is intended to influence or guide business behavior, in support of business policy that is formulated in response to an opportunity or threat. From the information system perspective, a business rule is a statement that defines or constrains some aspect of the business. It is intended to assert business structure or to control or influence the behavior of the business. ^[2]

From a practical standpoint, a business rule asserts a statement about the state of a business process or a directive describing changes in the state of a business process. More simply, a business rule dictates what happens when a sequence of inputs is applied to one or more well-described scenarios.

A rule is a statement that asserts some truth about the system, along with optional actions to be performed, depending on the assertion's truth value. Rules can be classified as falling into one of the following areas:

• Definitions and specifications, which provides a well-defined vocabulary for more complex rule specification. Rules in this class should enumerate the descriptive figures of speech used in describing business processes.

• Assertions, which are statements about entities within the system that express sensible observations about the business. Assertions describe relationships between entities and activities within the framework. Together, the definitions and assertions drive the construction of the logical data model within which the business rules operate.

• Constraints, which express unconditional conformance to a business statement; compared to a constraint, a data instance...