Business rules are explicit statements that define certain aspects of an organization’s operations.
- They govern how data is created, processed, managed, and maintained within a software system to ensure alignment with the policies, goals, and structure of the business.
- They ensure that the system operates correctly and consistently, enforcing policies that reflect real-world constraints, requirements, or decisions.
- They apply to both the logic of the system’s operations and the structure of the data it handles.
Examples of business rules include:
- “A customer must have at least one order.”
- “An employee’s age must be greater than or equal to 18.”
- “A student may register for a course only if prerequisites are completed.”
- “Preferred customers receive a 10% discount unless they have an overdue balance.”
In database design, these rules are often referred to as integrity constraints when they are used to ensure the validity and consistency of data (e.g., primary key constraints, foreign key constraints, check constraints).
Types of Business Rules:
Business rules can be categorized into three main types:
1.) Structural Assertions:
These are statements about static organizational structure, typically expressed through entities, attributes, and relationships. They define terms and facts that describe data and its structure.
- Example: “A student has a student name as an attribute.”
- Example: “A course is a module of instruction in a subject area.”
These are often represented in Entity-Relationship (E-R) diagrams, which visually show how data entities are connected.
2.) Action Assertions:
These rules govern the dynamic behavior of a system by defining constraints or controls on the actions that users or systems can perform.
- Example: “A student must have a GPA > 2.2 to pass the course.”
- Example: “A discount must not be applied if the account balance is overdue.”
These rules are commonly implemented in databases using triggers, stored procedures, or application-level validation logic to enforce data integrity during operations like insert, update, or delete.
Components of Action Assertions:
- User Rule: The business policy or rule to be enforced.
- Event: The operation that triggers the rule (e.g., insert, update, delete).
- Entity Name: The specific entity/table affected by the rule.
- Condition: A logical expression that must be satisfied.
- Action: The operation executed when the condition is met.
3.) Derivations:
These are rules that involve calculations, inferences, or transformations based on other known facts or data.
- Example: “A paycheck is calculated as hours worked multiplied by hourly rate minus deductions.”
- Example: “Total order value is the sum of all item prices in the order.”
These rules are used for automated computations and are often implemented through formulas, expressions, or computed fields.
Purpose and Importance of Business Rules:
- Ensure Data Integrity: Prevent invalid or inconsistent data from being entered or manipulated.
- Enforce Organizational Policies: Guarantee that systems reflect real-world business practices and constraints.
- Support Automation: Enable consistent automatic processing of calculations and validations.
- Improve Communication: Clearly define rules so that developers, analysts, and stakeholders understand and agree on system behavior.
- Enhance System Quality: Reduce errors, improve reliability, and promote maintainability.
