# Functional Requirements

# Functional Requirements Specification (FRS): {{PROJECT_NAME}}

> **Project:** {{PROJECT_NAME}}
> **Version:** {{VERSION}}
> **Date:** {{DATE}}
> **Author:** {{AUTHOR}}
> **Status:** Draft | In Review | Approved
> **Reviewers:** {{REVIEWERS}}

## Document History
| Version | Date | Author | Changes |
|---------|------|--------|---------|
| 0.1     | {{DATE}} | {{AUTHOR}} | Initial draft |

---

<!-- GUIDANCE: The FRS describes system behavior in detail — what the system does, not how it is built.
It bridges the BRD (business needs) and the Technical Spec (implementation).
Written by BA + Tech Lead. Every requirement must be testable and trace to a business requirement. -->

## 1. System Overview

<!-- GUIDANCE: Describe the system at a high level. What is it? Who uses it? What are its main capabilities?
Include a context diagram showing the system and its external interactions. -->

**System Name:** {{SYSTEM_NAME}}
**System Purpose:** {{PURPOSE_2_3_SENTENCES}}

**System Context Diagram:**

```mermaid
graph TB
    subgraph "{{SYSTEM_NAME}}"
        UI[Web / Mobile UI]
        API[Backend API]
        DB[(Database)]
    end
    U1[{{USER_TYPE_1}}] -->|Uses| UI
    U2[{{USER_TYPE_2}}] -->|Uses| UI
    API -->|Reads/Writes| DB
    API -->|Integrates| EXT1[{{EXTERNAL_SERVICE_1}}]
    API -->|Integrates| EXT2[{{EXTERNAL_SERVICE_2}}]
    ADM[Admin] -->|Manages| UI
```

---

## 2. Actors & Personas

<!-- GUIDANCE: Actors are all users and external systems that interact with the system.
Personas add context about who these users really are, which drives UX decisions. -->

| Actor ID | Actor Name | Type | Description | Access Level |
|----------|-----------|------|-------------|-------------|
| ACT-01 | {{ACTOR_NAME}} | Human / System | {{DESCRIPTION}} | {{ROLE/PERMISSIONS}} |
| ACT-02 | End User | Human | {{PERSONA_DESCRIPTION}} | Authenticated user |
| ACT-03 | Administrator | Human | Manages system configuration and users | Admin |
| ACT-04 | {{EXTERNAL_SYSTEM}} | System | External service integrated via API | System |

### Persona Detail

<!-- GUIDANCE: For each key human actor, add a brief persona card. -->

**Persona: {{PERSONA_NAME}}**
- **Role:** {{JOB_TITLE}}
- **Goal:** {{PRIMARY_GOAL_USING_SYSTEM}}
- **Pain Points:** {{CURRENT_FRUSTRATIONS}}
- **Tech Savviness:** Low / Medium / High
- **Frequency of Use:** Daily / Weekly / Monthly

---

## 3. Functional Requirements

<!-- GUIDANCE: Organize requirements by module/feature. Within each module:
- FR-XXX = unique ID (sequential across all modules)
- Priority = MoSCoW (Must/Should/Could/Won't for this release)
- Acceptance Criteria = Given/When/Then (testable conditions for done)
- Trace = BRD requirement ID this satisfies -->

### 3.1 Module: {{MODULE_1_NAME}}
<!-- GUIDANCE: e.g., Authentication, User Management, Dashboard, Reporting, Notifications -->

#### Module Overview
{{MODULE_DESCRIPTION}}

---

**FR-001: {{FEATURE_NAME}}**

| Attribute | Value |
|-----------|-------|
| Module | {{MODULE_1_NAME}} |
| Priority | Must Have |
| Trace | BR-{{XXX}} |
| UI Reference | `[Figma link or mockup filename]` |

**Description:**
{{FEATURE_DESCRIPTION_IN_BUSINESS_LANGUAGE}}

**Acceptance Criteria:**
- [ ] **Given** {{PRECONDITION}}, **when** {{USER_ACTION}}, **then** {{EXPECTED_RESULT}}
- [ ] **Given** {{PRECONDITION}}, **when** {{USER_ACTION}}, **then** {{EXPECTED_RESULT}}
- [ ] **Given** invalid input, **when** {{USER_ACTION}}, **then** {{ERROR_HANDLING}}

**Data Requirements:**
- Input: {{INPUT_DATA_FIELDS_AND_TYPES}}
- Output: {{OUTPUT_DATA}}
- Validation: {{VALIDATION_RULES}}

**Business Rules:**
- RUL-{{XX}}: {{APPLICABLE_BUSINESS_RULE}}

**Dependencies:** FR-{{XXX}}, DEP-{{XX}}

---

**FR-002: {{FEATURE_NAME}}**

| Attribute | Value |
|-----------|-------|
| Module | {{MODULE_1_NAME}} |
| Priority | Must Have |
| Trace | BR-{{XXX}} |
| UI Reference | |

**Description:**
{{FEATURE_DESCRIPTION}}

**Acceptance Criteria:**
- [ ] **Given** {{PRECONDITION}}, **when** {{USER_ACTION}}, **then** {{EXPECTED_RESULT}}
- [ ] **Given** {{PRECONDITION}}, **when** {{USER_ACTION}}, **then** {{EXPECTED_RESULT}}

**Data Requirements:**
- Input: {{INPUT}}
- Output: {{OUTPUT}}
- Validation: {{VALIDATION}}

**Business Rules:** {{APPLICABLE_RULES}}

**Dependencies:** {{DEPENDENCIES}}

---

### 3.2 Module: {{MODULE_2_NAME}}

#### Module Overview
{{MODULE_DESCRIPTION}}

---

**FR-010: {{FEATURE_NAME}}**

| Attribute | Value |
|-----------|-------|
| Module | {{MODULE_2_NAME}} |
| Priority | Must Have |
| Trace | BR-{{XXX}} |
| UI Reference | |

**Description:**
{{FEATURE_DESCRIPTION}}

**Acceptance Criteria:**
- [ ] **Given** {{PRECONDITION}}, **when** {{USER_ACTION}}, **then** {{EXPECTED_RESULT}}
- [ ] **Given** {{PRECONDITION}}, **when** {{USER_ACTION}}, **then** {{EXPECTED_RESULT}}

**Data Requirements:**
- Input: {{INPUT}}
- Output: {{OUTPUT}}
- Validation: {{VALIDATION}}

**Business Rules:** {{APPLICABLE_RULES}}

**Dependencies:** {{DEPENDENCIES}}

---

### 3.3 Module: Authentication & Authorization

<!-- GUIDANCE: Every system with user accounts needs this section. Adapt to the auth method used. -->

**FR-020: User Registration**
| Attribute | Value |
|-----------|-------|
| Priority | Must Have |
| Trace | BR-{{XXX}} |

**Description:** Users can create a new account using email and password.

**Acceptance Criteria:**
- [ ] **Given** a valid email and password (≥8 chars, 1 uppercase, 1 number), **when** user submits registration form, **then** account is created and confirmation email is sent
- [ ] **Given** an already-registered email, **when** user tries to register, **then** system shows "Email already in use" error
- [ ] **Given** password does not meet complexity rules, **when** user submits, **then** inline validation error shown before submit

**Data Requirements:**
- Input: email (unique), password, {{ADDITIONAL_FIELDS}}
- Output: user record, confirmation token
- Validation: email format, password complexity, duplicate check

---

**FR-021: User Login**
| Attribute | Value |
|-----------|-------|
| Priority | Must Have |
| Trace | BR-{{XXX}} |

**Description:** Authenticated users can log in with email and password.

**Acceptance Criteria:**
- [ ] **Given** valid credentials, **when** user submits login form, **then** user is authenticated and redirected to dashboard
- [ ] **Given** invalid credentials, **when** user submits, **then** generic error "Invalid email or password" is shown (no enumeration)
- [ ] **Given** 5 consecutive failed attempts, **when** user tries again, **then** account is temporarily locked for 15 minutes
- [ ] **Given** an authenticated session, **when** user is idle for 30 minutes, **then** session expires and user is redirected to login

---

### 3.4 Module: {{MODULE_N_NAME}}

**FR-030: {{FEATURE_NAME}}**
<!-- Add as many modules and features as needed following the pattern above -->

---

## 4. Use Case Diagrams

<!-- GUIDANCE: Use case diagrams show which actors can perform which actions.
Create one diagram per major module, or one overall diagram for simpler systems. -->

### 4.1 {{MODULE_1_NAME}} Use Cases

```mermaid
graph LR
    A1(({{ACTOR_1}})) --> UC1[FR-001: {{FEATURE}}]
    A1 --> UC2[FR-002: {{FEATURE}}]
    A2(({{ACTOR_2}})) --> UC3[FR-010: {{FEATURE}}]
    A2 --> UC4[FR-011: {{FEATURE}}]
    A3((Admin)) --> UC5[FR-020: {{FEATURE}}]
    A3 --> UC6[FR-021: {{FEATURE}}]
```

### 4.2 System-Level Use Case Overview

```mermaid
graph LR
    subgraph "{{SYSTEM_NAME}}"
        UC1[{{MODULE_1}} Functions]
        UC2[{{MODULE_2}} Functions]
        UC3[Auth Functions]
    end
    ACT1(({{ACTOR_1}})) --> UC1
    ACT1 --> UC3
    ACT2(({{ACTOR_2}})) --> UC2
    ACT2 --> UC3
    ACT3((Admin)) --> UC1
    ACT3 --> UC2
    ACT3 --> UC3
```

---

## 5. System Behavior Specifications

<!-- GUIDANCE: Document system-level behaviors that apply across multiple features.
These are not tied to a single feature but are fundamental to how the system operates. -->

### 5.1 Error Handling

- All user-facing errors must display a human-readable message (no stack traces)
- All errors must be logged with correlation ID, timestamp, user ID (if authenticated), and action
- Validation errors shown inline, adjacent to the invalid field
- System errors show generic message + contact info; full detail logged server-side only

### 5.2 Data Persistence

- All user-submitted data must be persisted within {{X}} seconds
- Optimistic UI updates must be rolled back if server confirmation fails
- All mutations (create/update/delete) must be audited with user ID and timestamp

### 5.3 Session & State

- Session timeout: {{X}} minutes of inactivity
- Concurrent session behavior: {{ALLOW/BLOCK/NOTIFY}}
- Browser refresh: application state must be restored from server

### 5.4 Notifications

- Email notifications: {{WHICH_EVENTS_TRIGGER_EMAILS}}
- In-app notifications: {{WHICH_EVENTS_TRIGGER_IN_APP}}
- Push notifications: {{IF_APPLICABLE}}
- Unsubscribe mechanism required for all marketing emails (GDPR)

### 5.5 Accessibility

- WCAG 2.1 Level AA compliance required
- Keyboard navigation for all interactive elements
- Screen reader compatibility (ARIA labels)
- Color contrast ratio ≥ 4.5:1

---

## 6. Requirements Summary Table

<!-- GUIDANCE: This summary table enables quick scanning of all requirements.
Update this table as requirements are added, changed, or approved. -->

| ID | Feature Name | Module | Priority | Status | Trace |
|----|-------------|--------|----------|--------|-------|
| FR-001 | {{FEATURE}} | {{MODULE}} | Must Have | Draft | BR-001 |
| FR-002 | | | | | |
| FR-010 | | | | | |
| FR-020 | User Registration | Auth | Must Have | Draft | BR-xxx |
| FR-021 | User Login | Auth | Must Have | Draft | BR-xxx |

**Requirements Count:**
- Must Have: {{COUNT}}
- Should Have: {{COUNT}}
- Could Have: {{COUNT}}
- Won't Have (this release): {{COUNT}}

---

## 7. Traceability to Business Requirements

<!-- GUIDANCE: Every functional requirement must trace to at least one business requirement from the BRD.
Orphaned requirements (no trace) should be questioned. -->

| FR ID | Feature Name | Business Requirement (BR ID) | Business Objective (BO ID) |
|-------|-------------|------------------------------|---------------------------|
| FR-001 | {{FEATURE}} | BR-{{XXX}} | BO-{{XX}} |
| FR-002 | | | |

> Full traceability matrix: `[requirements-traceability-matrix.md](requirements-traceability-matrix.md)`

---

## Approval

| Role | Name | Date | Signature |
|------|------|------|-----------|
| Author | | | |
| Reviewer | | | |
| Business Analyst | | | |
| Tech Lead | | | |
| Product Owner | | | |
| AI Director (John) | | | |
| Client Representative | | | |