Before understanding why rules are important within BPM, let's have a look at what a business rule is and what its characteristics are.
A business rule is an atomic assignment, which takes either true or false as its value. Rules have to be kept simple and not contain programming logic. Rules are declarative expressions, usually in an if-then style notation, consisting of a condition and an action. The action is only evaluated if the defined condition is met. Because of these characteristics, rules are easily readable and understandable for nontechnical people, regardless of the knowledge background, compared to the rules logic implemented in Java, for instance.
The following snippet shows a simple example for a business rule. It shows the characteristics previously discussed:
IF rentalCar.milesDriven > freeMiles THEN return (rentalCar.milesDriven - freeMiles) * 0.5
The rule, taken from the car rental scenario, is used during invoice...