Businesses are controlled by rules that regulate how the business operates and is structured. Rules ensure that the business is run according to predefined external (by laws or regulation) or internal (to make the business run as efficiently and profitably as possible) restriction or goal.

Business Rule can be defined as :

A Business Rule is a statement that can control or affect both the execution of a business process as well  as structure of the resources in the business.

Rules are identified by examining models, evaluating facts, talking with experts within the organization, studying laws and regulation surrounding the business, or studying how the business is run in practice.

There are basically three types of Business Rules:

I. Derivation II. Constraints III. Existence

Derivation: Rules that define how knowledge in one form transformed into other knowledge. A derivation can be either a computational rule, such as a formula for calculating a value, or an inference rule, meaning that if a certain fact is true, then another inference fact must also be true

Constraints: Rules that constrain either the possible structure or behavior of objects or process. Exp- the way objects are related to each other or the way object or process state change occurs

Existence: Rules that define when something may exist and when it should come into existence, that is, when an object is created or destroyed.