Extract Business Rules

extract-business-rules

Skill Type: Actuator (Requirements Disambiguation) Purpose: Extract BR-* business rules from REQ-* requirements Prerequisites: REQ-* requirement exists

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Agent Instructions

You are extracting business rules (BR-*) from requirements.

Business rules are:

• Validation rules (format, range, enum)
• Business logic (decisions, calculations, state machines)
• Error handling (what errors, what messages)
• Acceptance rules (what makes data valid/​invalid)

Goal: Identify rules precise enough for code autogeneration.

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BR-* Categories

1. Validation Rules

Format validation:

BR-001: Email validation
  - Format: regex ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$
  - Error: "Invalid email format"
  - Autogenerate: validate_email(email) -> Optional[str]

Range validation:

BR-010: Age validation
  - Minimum: 18
  - Maximum: 120
  - Error: "Age must be between 18 and 120"
  - Autogenerate: validate_age(age) -> Optional[str]

Enum validation:

BR-020: Card type validation
  - Allowed: ["Visa", "Mastercard", "Amex"]
  - Error: "Card type not supported"
  - Autogenerate: validate_card_type(type) -> Optional[str]

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2. Business Logic Rules

State machines:

BR-030: Account lockout logic
  - Max attempts: 3
  - Lockout duration: 15 minutes
  - Reset on success: Yes
  - States: active, locked, expired
  - Autogenerate: LockoutStateMachine class

Decision rules:

BR-040: Refund eligibility
  - Condition: purchase_date within 30 days AND product not digital
  - Result: eligible or not_eligible
  - Error: "Refunds only available within 30 days for physical products"
  - Autogenerate: is_refund_eligible() -> bool

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3. Error Handling Rules

BR-050: Error message format
  - Template: "{field} {error_type}. {help_text}"
  - Example: "Email invalid email format. Use format: [email protected]"
  - Autogenerate: format_error_message() function

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4. Data Transformation Rules

BR-060: Email normalization
  - Transform: Convert to lowercase
  - Trim: Remove leading/​trailing whitespace
  - Validate: After transformation
  - Autogenerate: normalize_email(email) -> str

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Extraction Process

Step 1: Parse Requirement

Read requirement and identify rule candidates:

• Look for: "must", "should", "required", "only", "between", "minimum", "maximum"
• Look for: formats, patterns, ranges, lists
• Look for: error messages, validation criteria

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Step 2: Create BR-* Specifications

Template:

BR-{ID}: {Rule Name}
  - Description: {What this rule does}
  - Specification: {Precise spec - regex, range, formula}
  - Error Message: "{User-facing error message}"
  - Autogenerate: {Yes/​No - can code be auto-generated?}
  - Dependencies: {Other BR-* this depends on}

Example:

BR-001: Email validation
  - Description: Validate email address format
  - Specification: regex ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$
  - Error Message: "Invalid email format"
  - Autogenerate: Yes
  - Dependencies: None

BR-002: Password length validation
  - Description: Ensure password meets minimum length
  - Specification: len(password) >= 12
  - Error Message: "Password must be at least 12 characters"
  - Autogenerate: Yes
  - Dependencies: None

BR-003: Password complexity validation
  - Description: Ensure password has required character types
  - Specification:
      has_uppercase: password contains [A-Z]
      has_lowercase: password contains [a-Z]
      has_number: password contains [0-9]
      has_special: password contains [!@#$%^&*]
  - Error Message: "Password must contain uppercase, lowercase, number, and special character"
  - Autogenerate: Yes
  - Dependencies: BR-002 (length must be checked first)

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Step 3: Number BR-* Sequentially

Rules:

• Start at BR-001
• Sequential within requirement
• Gaps OK if BR deleted later

Example:

<REQ-ID>:
  - BR-001: Email validation
  - BR-002: Password length
  - BR-003: Password complexity
  - BR-004: Email case handling
  - BR-005: Account lockout

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Output Format

[EXTRACT BUSINESS RULES - <REQ-ID>]

Requirement: User login with email and password

Business Rules Extracted:

Validation Rules (4):
  ✓ BR-001: Email validation (regex pattern)
  ✓ BR-002: Password minimum length (12 chars)
  ✓ BR-003: Password complexity (uppercase, lowercase, number, special)
  ✓ BR-004: Email case sensitivity (lowercase normalization)

Business Logic (1):
  ✓ BR-005: Account lockout (3 attempts, 15min duration)

Total: 5 business rules

Autogeneration Ready:
  ✓ BR-001 → validate_email()
  ✓ BR-002 → validate_password_length()
  ✓ BR-003 → validate_password_complexity()
  ✓ BR-004 → normalize_email()
  ✓ BR-005 → LockoutTracker class

Updated: docs/​requirements/​authentication.md
  Added: Business Rules section with 5 BR-*

✅ Business Rules Extraction Complete!

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Notes

Good BR- characteristics*:

• Specific: No ambiguity (regex, not "valid format")
• Testable: Can write test to verify
• Autogenerable: Can generate code from spec
• Independent: Each BR-* is self-contained

BR- vs Requirements*:

Requirement (REQ-*): High-level capability
  "User can log in with email and password"

Business Rules (BR-*): Low-level specifications
  BR-001: Email regex pattern
  BR-002: Password min 12 chars
  BR-003: Lockout after 3 attempts

Homeostasis Goal:

desired_state:
  all_requirements_have_business_rules: true
  all_br_autogenerable: true

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