What are business rules in COBOL?

Business rules in COBOL are specific constraints, calculations, and decision criteria that define how the application processes data, makes decisions, and enforces business requirements.

How do you implement business rules in COBOL?

Business rules are implemented using conditional statements, decision tables, validation routines, calculation logic, and rule-based processing structures in the Procedure Division.

What is a decision table in COBOL?

A decision table in COBOL is a structured approach to implementing complex business rules using conditional logic, lookup tables, and rule-based processing for multiple business scenarios.

How do you validate business rules in COBOL?

Business rule validation is implemented using validation routines, error checking, data integrity checks, and constraint enforcement throughout the application processing.

What are the benefits of rule-based programming in COBOL?

Benefits include maintainability, flexibility, testability, clear separation of business logic, easier rule modifications, and improved code organization.

How do you handle rule changes in COBOL applications?

Rule changes are handled through parameterization, configuration tables, modular design, and structured rule implementation that allows easy modification without code changes.

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COBOL Business Rules

Business rules in COBOL define the specific constraints, calculations, and decision criteria that govern how applications process data and make decisions. These rules implement business requirements, enforce data integrity, and ensure compliance with organizational policies.

Understanding Business Rules

Business rules are specific statements that define or constrain some aspect of the business. In COBOL, these rules are implemented as program logic that enforces business constraints, performs calculations, and makes decisions based on business requirements.

Types of Business Rules

1. Validation Rules

Validation rules ensure data integrity and enforce business constraints on input data and business operations.

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       WORKING-STORAGE SECTION.
       01 VALIDATION-RULES.
           05 MIN-ACCOUNT-BALANCE PIC 9(8)V99 VALUE 1000.
           05 MAX-TRANSACTION-AMT PIC 9(8)V99 VALUE 50000.
           05 VALID-CUSTOMER-TYPES PIC X(3) VALUE 'PSB'.
           05 MIN-CREDIT-SCORE    PIC 9(3) VALUE 300.
           05 MAX-CREDIT-SCORE    PIC 9(3) VALUE 850.
       
       01 VALIDATION-RESULTS.
           05 VALIDATION-ERRORS  PIC 9(2) VALUE 0.
           05 ERROR-FLAG        PIC X(1).
               88 VALIDATION-PASSED VALUE 'Y'.
               88 VALIDATION-FAILED VALUE 'N'.
       
       PROCEDURE DIVISION.
       VALIDATE-BUSINESS-RULES.
           MOVE 'Y' TO VALIDATION-FLAG
           MOVE 0 TO VALIDATION-ERRORS
           
           PERFORM VALIDATE-ACCOUNT-BALANCE
           PERFORM VALIDATE-TRANSACTION-AMOUNT
           PERFORM VALIDATE-CUSTOMER-TYPE
           PERFORM VALIDATE-CREDIT-SCORE
           
           IF VALIDATION-ERRORS > 0
               MOVE 'N' TO VALIDATION-FLAG
           END-IF.
       
       VALIDATE-ACCOUNT-BALANCE.
           IF ACCOUNT-BALANCE < MIN-ACCOUNT-BALANCE
               ADD 1 TO VALIDATION-ERRORS
               DISPLAY 'ERROR: Account below minimum balance'
           END-IF.
       
       VALIDATE-TRANSACTION-AMOUNT.
           IF TRANSACTION-AMOUNT > MAX-TRANSACTION-AMT
               ADD 1 TO VALIDATION-ERRORS
               DISPLAY 'ERROR: Transaction exceeds maximum amount'
           END-IF.

2. Calculation Rules

Calculation rules implement business formulas and mathematical operations required by business processes.

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       WORKING-STORAGE SECTION.
       01 CALCULATION-RULES.
           05 INTEREST-RATE      PIC 9(3)V9999 VALUE 0.0525.
           05 SERVICE-FEE-RATE   PIC 9(3)V9999 VALUE 0.0025.
           05 OVERDRAFT-FEE      PIC 9(4)V99 VALUE 25.00.
           05 MINIMUM-PAYMENT    PIC 9(3)V9999 VALUE 0.02.
       
       01 CALCULATION-RESULTS.
           05 MONTHLY-INTEREST   PIC 9(8)V99.
           05 SERVICE-FEE        PIC 9(8)V99.
           05 TOTAL-FEES        PIC 9(8)V99.
           05 MINIMUM-PAYMENT-AMT PIC 9(8)V99.
       
       PROCEDURE DIVISION.
       CALCULATE-BUSINESS-RULES.
           PERFORM CALCULATE-MONTHLY-INTEREST
           PERFORM CALCULATE-SERVICE-FEE
           PERFORM CALCULATE-MINIMUM-PAYMENT
           PERFORM CALCULATE-TOTAL-FEES.
       
       CALCULATE-MONTHLY-INTEREST.
           COMPUTE MONTHLY-INTEREST = 
               ACCOUNT-BALANCE * INTEREST-RATE / 12.
       
       CALCULATE-SERVICE-FEE.
           COMPUTE SERVICE-FEE = 
               ACCOUNT-BALANCE * SERVICE-FEE-RATE.
       
       CALCULATE-MINIMUM-PAYMENT.
           COMPUTE MINIMUM-PAYMENT-AMT = 
               ACCOUNT-BALANCE * MINIMUM-PAYMENT.
       
       CALCULATE-TOTAL-FEES.
           ADD MONTHLY-INTEREST SERVICE-FEE TO TOTAL-FEES.

3. Decision Rules

Decision rules implement business logic for making decisions based on specific criteria and conditions.

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       WORKING-STORAGE SECTION.
       01 DECISION-CRITERIA.
           05 CUSTOMER-TYPE      PIC X(1).
               88 PREMIUM-CUSTOMER VALUE 'P'.
               88 STANDARD-CUSTOMER VALUE 'S'.
               88 BASIC-CUSTOMER VALUE 'B'.
           05 ACCOUNT-BALANCE   PIC 9(8)V99.
           05 CREDIT-SCORE      PIC 9(3).
           05 TRANSACTION-HISTORY PIC 9(3).
       
       01 DECISION-RESULTS.
           05 APPROVAL-STATUS   PIC X(1).
               88 APPROVED VALUE 'Y'.
               88 DENIED VALUE 'N'.
               88 PENDING VALUE 'P'.
           05 APPROVAL-LIMIT    PIC 9(8)V99.
           05 APPROVAL-REASON   PIC X(50).
       
       PROCEDURE DIVISION.
       APPLY-DECISION-RULES.
           PERFORM EVALUATE-CUSTOMER-TYPE
           PERFORM CHECK-CREDIT-CRITERIA
           PERFORM DETERMINE-APPROVAL-LIMIT
           PERFORM FINALIZE-DECISION.
       
       EVALUATE-CUSTOMER-TYPE.
           EVALUATE CUSTOMER-TYPE
               WHEN 'P'
                   PERFORM PREMIUM-CUSTOMER-RULES
               WHEN 'S'
                   PERFORM STANDARD-CUSTOMER-RULES
               WHEN 'B'
                   PERFORM BASIC-CUSTOMER-RULES
               WHEN OTHER
                   MOVE 'N' TO APPROVAL-STATUS
                   MOVE 'INVALID CUSTOMER TYPE' TO APPROVAL-REASON
           END-EVALUATE.
       
       PREMIUM-CUSTOMER-RULES.
           IF CREDIT-SCORE >= 700 AND ACCOUNT-BALANCE >= 10000
               MOVE 'Y' TO APPROVAL-STATUS
               MOVE 100000 TO APPROVAL-LIMIT
               MOVE 'PREMIUM CUSTOMER APPROVED' TO APPROVAL-REASON
           ELSE
               MOVE 'P' TO APPROVAL-STATUS
               MOVE 'MANUAL REVIEW REQUIRED' TO APPROVAL-REASON
           END-IF.

Rule Implementation Patterns

1. Rule Tables

Use rule tables to implement complex business rules with multiple conditions and outcomes.

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       WORKING-STORAGE SECTION.
       01 RULE-TABLE.
           05 RULE-ENTRIES OCCURS 10 TIMES.
               10 RULE-ID        PIC 9(2).
               10 RULE-CONDITION PIC X(20).
               10 RULE-ACTION    PIC X(30).
               10 RULE-PRIORITY  PIC 9(1).
       
       01 RULE-PROCESSING.
           05 CURRENT-RULE      PIC 9(2).
           05 RULE-MATCHED      PIC X(1).
               88 RULE-FOUND VALUE 'Y'.
               88 RULE-NOT-FOUND VALUE 'N'.
       
       PROCEDURE DIVISION.
       PROCESS-RULE-TABLE.
           MOVE 1 TO CURRENT-RULE
           MOVE 'N' TO RULE-MATCHED
           
           PERFORM UNTIL CURRENT-RULE > 10 OR RULE-MATCHED = 'Y'
               PERFORM EVALUATE-RULE-CONDITION
               IF RULE-CONDITION(CURRENT-RULE) = 'MATCHED'
                   MOVE 'Y' TO RULE-MATCHED
                   PERFORM EXECUTE-RULE-ACTION
               ELSE
                   ADD 1 TO CURRENT-RULE
               END-IF
           END-PERFORM.

2. Configuration-Driven Rules

Implement rules using configuration parameters that can be modified without changing the program code.

Best Practices

Modularity: Separate rules into distinct paragraphs
Documentation: Document rule logic and business requirements
Testing: Test rules with various scenarios
Maintainability: Use clear naming and structure
Flexibility: Design for easy rule modifications
Error Handling: Implement comprehensive error handling

COBOL Business Rules

Understanding Business Rules

Types of Business Rules

1. Validation Rules

2. Calculation Rules

3. Decision Rules

Rule Implementation Patterns

1. Rule Tables

2. Configuration-Driven Rules

Best Practices

Business Logic

Decision Tables

Validation Logic

Conditional Logic

Rule Engine

Configuration Management