How do I implement complex business rules?

Break down complex rules into smaller, manageable conditions. Use EVALUATE statements and decision tables for clarity and maintainability.

What are decision trees in COBOL?

Hierarchical decision structures that process data through multiple levels of conditions, often representing complex business logic flows.

MainframeMaster

COBOL Conditional Processing

Q: What is conditional processing in COBOL?

The implementation of business rules and decision logic that determines how data is processed based on various conditions and criteria.

Conditional processing implements business rules and decision logic that determines how data is processed. Learn to build decision trees, implement complex business rules, and create maintainable conditional logic.

Business Rule Implementation

cobol

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
       *> Credit approval business rules
       IF CUSTOMER-INCOME >= 50000 AND CREDIT-SCORE >= 700
           MOVE 'APPROVED' TO LOAN-STATUS
           MOVE 100000 TO MAX-LOAN-AMOUNT
           DISPLAY 'Loan approved - High income, good credit'
       ELSE IF CUSTOMER-INCOME >= 30000 AND CREDIT-SCORE >= 650
           MOVE 'APPROVED' TO LOAN-STATUS
           MOVE 50000 TO MAX-LOAN-AMOUNT
           DISPLAY 'Loan approved - Medium income, fair credit'
       ELSE IF CUSTOMER-INCOME >= 20000 AND CREDIT-SCORE >= 600
           MOVE 'CONDITIONAL' TO LOAN-STATUS
           MOVE 25000 TO MAX-LOAN-AMOUNT
           DISPLAY 'Conditional approval - Low income, poor credit'
       ELSE
           MOVE 'DENIED' TO LOAN-STATUS
           MOVE 0 TO MAX-LOAN-AMOUNT
           DISPLAY 'Loan denied - Insufficient income or credit'
       END-IF.

Implement business rules as clear, hierarchical conditions. Start with the most favorable conditions and work down to less favorable ones. Each condition should result in a specific business outcome with appropriate actions.

Decision Tree Processing

cobol

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
       *> Customer classification decision tree
       EVALUATE TRUE
           WHEN CUSTOMER-TYPE = 'INDIVIDUAL'
               EVALUATE TRUE
                   WHEN CUSTOMER-AGE >= 65
                       PERFORM PROCESS-SENIOR-INDIVIDUAL
                   WHEN CUSTOMER-AGE >= 18
                       PERFORM PROCESS-ADULT-INDIVIDUAL
                   WHEN OTHER
                       PERFORM PROCESS-MINOR-INDIVIDUAL
               END-EVALUATE
           WHEN CUSTOMER-TYPE = 'CORPORATE'
               EVALUATE TRUE
                   WHEN COMPANY-SIZE = 'LARGE'
                       PERFORM PROCESS-LARGE-CORPORATE
                   WHEN COMPANY-SIZE = 'MEDIUM'
                       PERFORM PROCESS-MEDIUM-CORPORATE
                   WHEN COMPANY-SIZE = 'SMALL'
                       PERFORM PROCESS-SMALL-CORPORATE
                   WHEN OTHER
                       PERFORM PROCESS-UNKNOWN-CORPORATE
               END-EVALUATE
           WHEN OTHER
               PERFORM PROCESS-UNKNOWN-CUSTOMER-TYPE
       END-EVALUATE.

Build decision trees using nested EVALUATE statements. Each level of the tree represents a different decision point. This structure makes complex business logic clear and maintainable.

Rule-Based Processing

cobol

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
       *> Pricing rules based on multiple factors
       MOVE 0 TO DISCOUNT-PERCENTAGE
       
       *> Volume discount rule
       IF ORDER-QUANTITY >= 1000
           ADD 10 TO DISCOUNT-PERCENTAGE
       ELSE IF ORDER-QUANTITY >= 500
           ADD 5 TO DISCOUNT-PERCENTAGE
       END-IF.
       
       *> Customer type discount rule
       IF CUSTOMER-TYPE = 'PREMIUM'
           ADD 5 TO DISCOUNT-PERCENTAGE
       ELSE IF CUSTOMER-TYPE = 'GOLD'
           ADD 3 TO DISCOUNT-PERCENTAGE
       END-IF.
       
       *> Payment terms discount rule
       IF PAYMENT-TERMS = 'CASH'
           ADD 2 TO DISCOUNT-PERCENTAGE
       END-IF.
       
       *> Apply maximum discount limit
       IF DISCOUNT-PERCENTAGE > 15
           MOVE 15 TO DISCOUNT-PERCENTAGE
       END-IF.

Implement rule-based processing by applying multiple independent rules that accumulate results. Each rule contributes to the final outcome. Use clear variable names and comments to document each rule's purpose.

Conditional Data Transformation

cobol

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
       *> Transform data based on business rules
       IF TRANSACTION-TYPE = 'DEPOSIT'
           ADD TRANSACTION-AMOUNT TO ACCOUNT-BALANCE
           MOVE 'CREDIT' TO TRANSACTION-CLASSIFICATION
       ELSE IF TRANSACTION-TYPE = 'WITHDRAWAL'
           IF ACCOUNT-BALANCE >= TRANSACTION-AMOUNT
               SUBTRACT TRANSACTION-AMOUNT FROM ACCOUNT-BALANCE
               MOVE 'DEBIT' TO TRANSACTION-CLASSIFICATION
           ELSE
               MOVE 'INSUFFICIENT-FUNDS' TO TRANSACTION-CLASSIFICATION
               PERFORM HANDLE-INSUFFICIENT-FUNDS
           END-IF
       ELSE IF TRANSACTION-TYPE = 'TRANSFER'
           PERFORM PROCESS-TRANSFER-TRANSACTION
       ELSE
           MOVE 'INVALID-TYPE' TO TRANSACTION-CLASSIFICATION
           PERFORM HANDLE-INVALID-TRANSACTION
       END-IF.

Use conditional processing to transform data based on business rules. Each condition results in different data transformations and classifications. Include error handling for invalid conditions.

Dynamic Processing Rules

cobol

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
       *> Processing rules that change based on context
       IF CURRENT-DATE > CUTOFF-DATE
           MOVE 'NEW-RULES' TO RULE-VERSION
           PERFORM APPLY-NEW-PROCESSING-RULES
       ELSE
           MOVE 'OLD-RULES' TO RULE-VERSION
           PERFORM APPLY-LEGACY-PROCESSING-RULES
       END-IF.
       
       *> Apply rules based on version
       EVALUATE RULE-VERSION
           WHEN 'NEW-RULES'
               PERFORM PROCESS-WITH-NEW-RULES
           WHEN 'OLD-RULES'
               PERFORM PROCESS-WITH-OLD-RULES
           WHEN OTHER
               PERFORM PROCESS-WITH-DEFAULT-RULES
       END-EVALUATE.

Implement dynamic processing rules that change based on context, dates, or other factors. Use rule versioning to handle different processing requirements. This allows for flexible business rule implementation.

Error Handling in Conditional Processing

cobol

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
       *> Comprehensive error handling
       IF INPUT-DATA IS NOT NUMERIC
           MOVE 'INVALID-NUMERIC' TO ERROR-CODE
           PERFORM LOG-ERROR
           PERFORM ERROR-HANDLING
       ELSE IF INPUT-DATA < 0
           MOVE 'NEGATIVE-VALUE' TO ERROR-CODE
           PERFORM LOG-ERROR
           PERFORM ERROR-HANDLING
       ELSE IF INPUT-DATA > MAX-VALUE
           MOVE 'VALUE-TOO-LARGE' TO ERROR-CODE
           PERFORM LOG-ERROR
           PERFORM ERROR-HANDLING
       ELSE
           MOVE 'VALID' TO ERROR-CODE
           PERFORM PROCESS-VALID-DATA
       END-IF.

Include comprehensive error handling in conditional processing. Check for invalid data types, ranges, and business rule violations. Log errors for analysis and provide meaningful error codes for troubleshooting.

Structure business rules hierarchically from most to least favorable.
Use decision trees for complex multi-level business logic.
Implement rule-based processing with accumulative results.
Include comprehensive error handling for all conditions.
Document business rules clearly with comments and meaningful variable names.

Conditional Logic

Decision making patterns

Business Rules

Implementing business logic