Create comprehensive Functional Requirements Specifications (FRS) that provide detailed, technical requirements for development teams to implement business solutions.
When to Use
After BRD approval
Before development begins
When technical teams need detailed specifications
For complex features requiring detailed documentation
FR-[MODULE]-[NUMBER]: [Requirement Title]
Description: [Detailed description of what the system shall do]
Business Rule: [Any business logic or rules]
Input: [What data/triggers initiate this function]
Process: [Step-by-step what the system does]
Output: [What the system produces/displays]
Acceptance Criteria:
- [Specific, testable criterion 1]
- [Specific, testable criterion 2]
UI/UX Notes: [Any UI specifications, wireframe references]
Dependencies: [Other requirements this depends on]
Priority: Must Have | Should Have | Could Have
Complexity: Low | Medium | High
Example - E-commerce Checkout :
FR-CHK-001: Guest Checkout
Description: System shall allow users to complete purchase without creating an account
Business Rule:
- Guest users must provide email for order confirmation
- After purchase, system shall offer account creation
- Guest checkout not available for orders > $5000
Input: User clicks "Checkout as Guest" button
Process:
1. System validates cart is not empty
2. System checks order total < $5000
3. System displays shipping address form
4. System validates address using address verification API
5. System displays shipping options with real-time pricing
6. System displays payment form
7. System processes payment via Stripe
8. System creates order record with guest flag
9. System sends confirmation email
10. System displays order confirmation page with option to create account
Output:
- Order confirmation number
- Email confirmation sent
- Order record created in database
Acceptance Criteria:
- Guest can complete checkout in < 2 minutes
- All form fields have proper validation
- Address verification catches invalid addresses
- Payment processing completes in < 5 seconds
- Confirmation email sent within 1 minute
- Order appears in admin system immediately
UI/UX Notes: See Figma wireframes (link)
- Single-page checkout design
- Progress indicator at top
- Order summary sticky on right side
- Mobile-responsive layout
Dependencies: FR-PAY-001 (Payment Processing), FR-ORD-001 (Order Creation)
Priority: Must Have
Complexity: High
4. Data Requirements
Entity Definitions :
Data entities and attributes
Data types and constraints
Relationships between entities
Data validation rules
Example :
Entity: Order
Attributes:
- order_id (UUID, Primary Key, Required, Auto-generated)
- customer_id (UUID, Foreign Key to Customer, Optional for guest)
- order_number (String, Unique, Format: ORD-YYYYMMDD-XXXX)
- order_date (DateTime, Required, Default: Current timestamp)
- status (Enum, Required, Values: pending|processing|shipped|delivered|cancelled)
- subtotal (Decimal(10,2), Required, Min: 0.01)
- tax (Decimal(10,2), Required, Min: 0)
- shipping_cost (Decimal(10,2), Required, Min: 0)
- total (Decimal(10,2), Required, Calculated: subtotal + tax + shipping_cost)
- shipping_address (JSON, Required)
- billing_address (JSON, Required)
- payment_method (String, Required)
- payment_status (Enum, Required, Values: pending|authorized|captured|failed|refunded)
- created_at (DateTime, Required, Auto-generated)
- updated_at (DateTime, Required, Auto-updated)
Relationships:
- One Order has many OrderItems
- One Order belongs to one Customer (optional)
- One Order has one Payment
Business Rules:
- Order number must be unique
- Total must equal subtotal + tax + shipping_cost
- Status transitions: pending → processing → shipped → delivered
- Cancelled orders cannot be modified
5. Integration Requirements
For Each Integration :
External system name and purpose
Integration type (API, File, Real-time, Batch)
Data flow direction
Authentication method
Error handling
Frequency/timing
Example :
INT-001: Stripe Payment Gateway Integration
Purpose: Process credit card payments securely
Type: REST API, Real-time
Direction: Bidirectional
- Outbound: Payment intent creation, charge capture
- Inbound: Payment confirmation, webhook notifications
Authentication: API Key (Secret key for server, Publishable key for client)
Endpoints Used:
- POST /v1/payment_intents (Create payment intent)
- POST /v1/payment_intents/{id}/confirm (Confirm payment)
- POST /v1/refunds (Process refund)
Data Mapping:
- Order.total → PaymentIntent.amount
- Order.currency → PaymentIntent.currency
- Customer.email → PaymentIntent.receipt_email
Error Handling:
- Network timeout (30 seconds): Retry up to 3 times with exponential backoff
- Payment declined: Display user-friendly error, log details
- API error: Fallback to manual payment processing, alert admin
Webhooks:
- payment_intent.succeeded → Update order status to "processing"
- payment_intent.payment_failed → Update order status to "failed", notify customer
- charge.refunded → Update order status to "refunded"
SLA: 99.9% uptime, < 2 second response time
Testing: Use Stripe test mode with test card numbers
6. Business Rules
Document all business logic and rules:
Example :
BR-001: Shipping Cost Calculation
- Orders < $50: Standard shipping $5.99, Express $12.99
- Orders $50-$99: Standard shipping $3.99, Express $9.99
- Orders ≥ $100: Free standard shipping, Express $7.99
- International orders: Calculated by weight and destination
- Alaska/Hawaii: Add $10 to standard rates
BR-002: Discount Application
- Only one promo code per order
- Promo codes cannot be combined with sale items
- Employee discount (20%) can be combined with promo codes
- Discounts applied before tax calculation
- Minimum order value may apply per promo code
BR-003: Inventory Reservation
- Items reserved for 15 minutes when added to cart
- Reservation extended by 15 minutes on each cart update
- Reservation released after 15 minutes of inactivity
- Out-of-stock items cannot be added to cart
- Backorder items can be added if enabled for product
7. UI/UX Specifications
Screen layouts and wireframes
User workflows and navigation
Form field specifications
Validation messages
Responsive design requirements
Accessibility requirements
Example :
Screen: Checkout Page
Layout: Single-page design with 3 sections
1. Shipping Information (left column)
2. Payment Information (left column, below shipping)
3. Order Summary (right column, sticky)
Shipping Information Fields:
- Email (required, email validation, max 100 chars)
- Full Name (required, min 2 chars, max 100 chars)
- Address Line 1 (required, max 100 chars)
- Address Line 2 (optional, max 100 chars)
- City (required, max 50 chars)
- State/Province (required, dropdown)
- ZIP/Postal Code (required, format validation based on country)
- Country (required, dropdown, default: US)
- Phone (required, phone format validation)
Validation:
- Real-time validation on blur
- Error messages displayed below field in red
- Submit button disabled until all required fields valid
Error Messages:
- Email: "Please enter a valid email address"
- Name: "Name must be at least 2 characters"
- ZIP: "Please enter a valid ZIP code"
Responsive:
- Desktop: 2-column layout
- Tablet: 2-column layout, narrower
- Mobile: Single column, order summary collapsible
Accessibility:
- All form fields have labels
- Error messages associated with fields (aria-describedby)
- Keyboard navigation support
- Screen reader compatible
- Color contrast ratio ≥ 4.5:1
8. Non-Functional Requirements
Performance requirements (response time, throughput)
