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What Is a Business Rule?

A business rule is a statement that defines or constrains some aspect of an organization. It is intended to assert structure or to control or influence the behavior of the organization. A good business rule is atomic and declarative. Atomic implies that each rule is made simple by dividing complex and compound rules into simpler rules in such a way that the meaning is not lost. Declarative implies that a rule may only state what the rule is, but not how it is implemented.

Business Rule Taxonomy

Presentation Rules specify the user interface aspect of an application

Example: Passwords must not be displayed

Constraints specify the validation checks on the data. There are two kinds of constraints: State and Transition

State constraints define legal states and values

Example 1: Account type can only be Savings or Checking

Example 2: Total owed <= Credit Limit

Transition constraints define legal transitions or changes from one legal state to another

Example: Allow transition from Unmarried to Married state but not to Divorced or Widowed

There are two kinds of derivations: Computation and Inference

A Computation is a formula to compute one value from others

Example 1: Sales Tax = Order Amount *Tax Rate

Example 2: Total owed = Sum of total values of unpaid orders

An inference is a rule to infer additional facts based on certain, given facts

Example: A customer is a preferred customer if total amount purchased > $100,000

Stimulus/Response is a combination of a triggering event (the stimulus) and a triggered action (the response)

Example 1: When an order is deleted, delete all it’s order items

Example 2: If there is insufficient funds to honor a check, charge the account a NSF fee of $25

Process rules define business processes and workflow

Example 2: Year end report generation and archival of old data

Example 1: Obtain credit approval before order can be shipped

Security and audit rules define permissions to information and tracking of who, what, and when of information retrieval and modification

Example: Employee benefit information is accessible only to employee and accounts personnel