Answer.

Business rules are established formal or informal standards by a company that define the order of operations, decision-making, calculations, communications, and information processing.

A business analyst identifies, analyzes, and documents them to ensure that the future system or process complies with the company's requirements and laws. Rules can be simple (e.g., "discounts are only provided to loyal customers") or complex ("automatic bonuses are granted only upon meeting a series of conditions").

Properly describing business rules guarantees:

• Alignment of the system's business logic with real processes.
• Consistency of requirements across different systems and departments.
• Simplification of software modernization, testing, and support.

Key features:

• Not all requirements are business rules. Some are limitations on implementation or integration.
• Business rules frequently change, so it is essential to separate them from code and maintain them in documentation.
• The language of formulations should be unambiguous and understandable to both the business and technical specialists.

Tricky Questions.

Are business rules always the same as business requirements?

No, business requirements define the goal to be achieved, while business rules are the constraints or methods to reach that goal. For example, the requirement may be "increase sales by 10%", while the business rule may be "give a discount of no more than 5% to new customers".

Can business logic be implemented without analyzing and formalizing business rules?

No, because non-formalized rules lead to ambiguities, errors in process automation, and violations of company regulations.

Where should the description of business rules be stored: only in the specifications or also in the system's code?

The description of business rules should be contained in project documentation (e.g., in requirements or a separate rule registry) and reflected in the system's business logic, but the primary source should be the document, not the code.

Common Mistakes and Anti-Patterns.

• Formulation of business rules in overly general or ambiguous terms.
• Duplication of business rules in different sections of documentation.
• Insufficient detail when one rule inadvertently covers different cases.
• Leaving business rules as "default" without explicit description (silent knowledge).

Example from Life.

Negative case:

• In a project to automate loan applications, managers duplicated business rules only verbally, without documenting them in the specifications, explaining to different developers orally — resulting in 3 different implementations of one scenario. Pros: Quickly launched MVP; minimized time for coordination. Cons: Discrepancies in logic across different scenarios, problems with automation, conflict between departments.

Positive case:

• For the loan approval task, the business analyst created a registry of business rules for all application types, coordinated with a lawyer and IT. Implementation took a bit longer, but the rules were clear to everyone. Pros: Clarity of business logic, minimized errors in automation. Cons: More time spent on preparing initial documentation.