According to the International Institute of Business Analysis (IIBA), a Business Rule is a precise, actionable and verifiable directive under the control of an organization which supports a business policy. Business Rules are derived from Business policies. Business policies however are non-actionable directives which support Business goals. Business Rules originate from three components namely, terms, facts and rules. Terms stand for clear definition, facts feed terms, and rules feed facts.
Characteristics of good Business Rules:
Business Rules should be atomic. They should be expressed in a granular format and should be as declarative as possible. A Business rule should always be framed as a precise statement defining a term, fact, and a constraint. Business Rules guide process flow or how the system works. A Business rule should be isolated from the process implementing it. Market experts recommend that BAs should isolate the process flow from what's known, meaning the process should be separated from the various Business Rules. This guarantees that changes to a Business rule can be made without changing the related process. Since rules are neither process nor procedure, they should not be contained in processes themselves.