Business Rules

Business rules are the core of any enterprise system. Collectively, they define how an organization functions. A correctly modeled set of business rules captures the various aspects of the organization in terms of policy, strategy, and procedure. By implementing these business rules, an IT system ensures a company's strategic initiatives are fully realized.

What Is a Business Rule?

A business rule is a statement or directive that defines, constrains, or controls some aspect of the business. It both asserts business structure and dictates business behavior.

The rules themselves are domain specific and range from the mundane to the exotic. Some examples include the following:

1. Stock items must be replenished when levels drop below 5 percent.

2. All creditors paying invoices within 30 days of billing will receive a 10 percent discount.

3. Jet aircraft are not permitted to land on grass runways.

Let's take a closer look at the structure of the common business rule.

Structure of a Business Rule

Most business rules can be specified using a syntax that is familiar to all developers. The structure of the business rule is one of a condition, followed by an action to be acted upon if the condition is met. Thus, business rules can be defined in terms of an "if ... then ..." style of construct.

The previous examples can be rewritten using this syntax:

1. If stock levels fall below 5 percent, then replenish the stock.

2. If an invoice is paid within 30 days of billing, then the price is discounted by 10 percent.

3. If you are flying a jet aircraft and the airport runway has a grass surface, then divert to another airport.

Though business rules have a simple structure, they are liable to change, making them dynamic in nature.

Dynamic Nature of Business Rules

Companies today face relentless market competition, and consequently many organizations are finding that agility is an essential survival trait. An agile company is one that can respond quickly to changes in the marketplace by making changes to core policy, strategy, and operational procedures. As the business rules define all of these behaviors, the rules themselves cannot be static. Instead, such rules are dynamic by their very nature and must be maintained in a format whereby they can be readily changed.

Consider the example of the rule that specifies a discount is to be given to all customers paying their bills within 30 days. In this example, the company instigating the rule may wish to reward customers with air points with a nominated airline instead of a cash discount. Alternatively, the company may offer a 10% discount to all customers who pay their account using direct debit.