# Product Requirements Document: Library Management System

## 1. Overview

The Library Management System is a comprehensive digital solution designed to streamline the operations of small to medium-sized libraries. The application enables librarians to manage book inventory, track member registrations, process book loans and returns, handle reservations, and monitor overdue items. The system provides both staff-facing administrative tools and member-facing features for browsing the catalog and managing their borrowing activity.

## 2. User Roles

### 2.1 Administrator
- Full system access and configuration capabilities
- Manage librarian accounts (create, update, deactivate)
- Configure system settings (loan periods, fine rates, library information)
- Generate comprehensive reports and analytics
- Manage book catalog (add, edit, delete books and authors)
- Override fines and extend loan periods
- Access audit logs and system activity

### 2.2 Librarian
- Manage member accounts (create, update, suspend, reactivate)
- Process book checkouts and returns
- Add and update books in the catalog
- Manage book reservations
- Process fine payments
- Search and browse the complete catalog
- View member borrowing history
- Generate standard reports

### 2.3 Member
- Browse and search the book catalog
- View own borrowing history and current loans
- Reserve available books
- View outstanding fines and payment history
- Update own profile information (contact details, password)
- Renew eligible loans
- View reservation queue status

### 2.4 Guest (Unauthenticated User)
- Browse public book catalog
- Search for books by title, author, or ISBN
- View book availability status
- Register for a new member account

## 3. Core Entities

### 3.1 User
Base entity representing any system user with authentication credentials, including personal information, role assignment, and account status.

### 3.2 Member
Extension of User representing library members who can borrow books, with membership details, borrowing limits, and account standing.

### 3.3 Librarian
Extension of User representing library staff with administrative privileges and employee information.

### 3.4 Administrator
Extension of User representing system administrators with full access rights.

### 3.5 Book
Physical or digital item in the library collection, including bibliographic information (title, ISBN, publication details), categorization, and current availability status.

### 3.6 Author
Creator of books, containing biographical information and associated works in the library collection.

### 3.7 Category
Classification system for organizing books by subject, genre, or topic.

### 3.8 Publisher
Publishing company information associated with books.

### 3.9 Loan
Transaction record representing a book borrowed by a member, including checkout date, due date, return date, and renewal history.

### 3.10 Reservation
Request by a member to borrow a book that is currently unavailable, including queue position and notification status.

### 3.11 Fine
Financial penalty assessed to a member for overdue books or damaged items, including amount, reason, payment status, and transaction history.

### 3.12 Payment
Financial transaction record for fine payments, including amount, payment method, date, and processing staff.

### 3.13 Review
Member-submitted rating and written review of a book they have borrowed.

### 3.14 Notification
System-generated or manual message sent to members regarding due dates, reservations, fines, or announcements.

### 3.15 AuditLog
System activity record tracking important actions, user responsible, timestamp, and affected entities for compliance and troubleshooting.

## 4. Entity Relationships

### 4.1 User Relationships
- **User → Member/Librarian/Administrator**: One-to-one (inheritance/specialization)
- **User → AuditLog**: One-to-many (one user performs many actions)

### 4.2 Book Relationships
- **Book → Author**: Many-to-many (a book can have multiple authors; an author can write multiple books)
- **Book → Category**: Many-to-many (a book can belong to multiple categories; a category contains multiple books)
- **Book → Publisher**: Many-to-one (a book has one publisher; a publisher publishes many books)
- **Book → Loan**: One-to-many (a book can be loaned multiple times over its lifetime)
- **Book → Reservation**: One-to-many (a book can have multiple reservations)
- **Book → Review**: One-to-many (a book can have multiple reviews)

### 4.3 Member Relationships
- **Member → Loan**: One-to-many (a member can have multiple loans)
- **Member → Reservation**: One-to-many (a member can have multiple reservations)
- **Member → Fine**: One-to-many (a member can have multiple fines)
- **Member → Payment**: One-to-many (a member can make multiple payments)
- **Member → Review**: One-to-many (a member can write multiple reviews)
- **Member → Notification**: One-to-many (a member receives multiple notifications)

### 4.4 Loan Relationships
- **Loan → Book**: Many-to-one (multiple loans reference one book)
- **Loan → Member**: Many-to-one (multiple loans belong to one member)
- **Loan → Fine**: One-to-many (a loan can generate multiple fines)

### 4.5 Fine Relationships
- **Fine → Payment**: One-to-many (a fine can be paid through multiple partial payments)
- **Fine → Member**: Many-to-one (multiple fines belong to one member)
- **Fine → Loan**: Many-to-one (multiple fines can be associated with one loan)

### 4.6 Other Relationships
- **Payment → Librarian**: Many-to-one (payments are processed by librarians)
- **Reservation → Book**: Many-to-one (multiple reservations for one book)
- **Reservation → Member**: Many-to-one (multiple reservations by one member)
- **Review → Book**: Many-to-one (multiple reviews for one book)
- **Review → Member**: Many-to-one (multiple reviews by one member)

## 5. Key Workflows

### 5.1 Member Registration Workflow
1. Guest navigates to registration page
2. Guest fills out registration form (name, email, phone, address, password)
3. System validates input data (email format, required fields, password strength)
4. System checks for duplicate email addresses
5. System creates new Member account with "Pending" status
6. System generates member ID/card number
7. Librarian reviews and approves the registration
8. System updates member status to "Active"
9. System sends welcome notification to member with login credentials
10. Member can now log in and use the system

### 5.2 Book Checkout Workflow
1. Member brings book(s) to circulation desk or requests checkout
2. Librarian scans/enters member ID
3. System verifies member status (active, not suspended, no excessive fines)
4. System checks member's current loan count against borrowing limit
5. Librarian scans/enters book ISBN or ID
6. System verifies book availability (not already on loan, not reserved by another member)
7. System creates Loan record with checkout date and calculated due date
8. System updates book status to "On Loan"
9. System decrements member's available borrowing quota
10. System generates checkout receipt
11. System sends due date reminder notification to member
12. Librarian hands book to member

### 5.3 Book Return Workflow
1. Member returns book(s) to library
2. Librarian scans/enters book ID
3. System retrieves active Loan record for the book
4. System calculates if return is overdue
5. If overdue:
   - System calculates fine amount based on days overdue and daily rate
   - System creates Fine record associated with the loan and member
   - System notifies member of fine
6. System updates Loan record with return date and status "Returned"
7. System updates book status to "Available"
8. System increments member's available borrowing quota
9. System checks for active Reservations for the returned book
10. If reservation exists:
    - System updates book status to "Reserved"
    - System notifies next member in reservation queue
    - System sets hold expiration date (e.g., 3 days to pick up)
11. System generates return receipt
12. Librarian places book on shelf or hold shelf

### 5.4 Book Reservation Workflow
1. Member searches for a book in the catalog
2. Member views book details and sees it's currently on loan
3. Member clicks "Reserve this book" button
4. System checks member's reservation limit (e.g., max 5 active reservations)
5. System checks if member already has an active reservation for this book
6. System creates Reservation record with current date and "Active" status
7. System calculates queue position based on existing reservations
8. System displays confirmation with estimated availability date
9. System sends confirmation notification to member
10. When book becomes available:
    - System updates reservation status to "Ready for Pickup"
    - System updates book status to "Reserved"
    - System sends notification to member
    - System sets hold expiration date
11. Member picks up book within hold period, triggering checkout workflow
12. If not picked up by expiration:
    - System cancels reservation
    - System moves to next member in queue or marks book as "Available"

### 5.5 Loan Renewal Workflow
1. Member logs into account or visits circulation desk
2. Member selects loan to renew from active loans list
3. System validates renewal eligibility:
   - Book is not reserved by another member
   - Loan has not exceeded maximum renewal count (e.g., 2 renewals)
   - Member has no excessive overdue fines
   - Book is not overdue
4. If eligible:
   - System updates loan due date (extends by standard loan period)
   - System increments renewal count
   - System logs renewal action
   - System sends confirmation notification with new due date
5. If not eligible:
   - System displays reason for denial
   - System suggests alternative actions (pay fines, return book, etc.)

### 5.6 Fine Payment Workflow
1. Member views outstanding fines in their account or at circulation desk
2. Member initiates payment (online or in-person)
3. Librarian or system displays total amount due
4. Member selects fines to pay (can pay partial or full amount)
5. Member provides payment (cash, card, online payment)
6. Librarian/system processes payment
7. System creates Payment record with amount, method, and date
8. System updates Fine record(s) payment status:
   - "Paid" if fully paid
   - "Partially Paid" if partial payment
   - Updates remaining balance
9. System generates payment receipt
10. System sends payment confirmation notification to member
11. If member was suspended due to fines and balance is now acceptable:
    - System updates member status to "Active"
    - System sends reactivation notification

### 5.7 Book Acquisition Workflow
1. Librarian/Administrator navigates to "Add New Book" form
2. Librarian enters or imports book details (ISBN, title, author, publisher, etc.)
3. System checks for duplicate ISBN in catalog
4. If ISBN exists, system prompts to add another copy instead
5. Librarian selects or creates Author record(s)
6. Librarian selects or creates Publisher record
7. Librarian assigns Categories
8. Librarian enters physical details (location, shelf number, condition)
9. Librarian sets book status (Available, Processing, etc.)
10. System validates all required fields
11. System generates unique book ID/barcode
12. System creates Book record
13. System logs acquisition in AuditLog
14. System displays confirmation with book details
15. Librarian prints barcode label and processes physical book

## 6. Features & Requirements

### 6.1 Authentication & Authorization Module

#### 6.1.1 User Authentication
- **REQ-AUTH-001**: System shall provide secure login with email and password
- **REQ-AUTH-002**: System shall implement password hashing using industry-standard algorithms (bcrypt, Argon2)
- **REQ-AUTH-003**: System shall enforce password complexity requirements (minimum 8 characters, mix of letters, numbers, special characters)
- **REQ-AUTH-004**: System shall provide "Forgot Password" functionality with email-based reset
- **REQ-AUTH-005**: System shall implement session management with configurable timeout (default 30 minutes of inactivity)
- **REQ-AUTH-006**: System shall support logout functionality that invalidates session tokens
- **REQ-AUTH-007**: System shall lock accounts after 5 consecutive failed login attempts
- **REQ-AUTH-008**: System shall log all authentication events (successful logins, failures, logouts)

#### 6.1.2 Authorization & Access Control
- **REQ-AUTH-009**: System shall implement role-based access control (RBAC)
- **REQ-AUTH-010**: System shall restrict feature access based on user role
- **REQ-AUTH-011**: System shall prevent privilege escalation attempts
- **REQ-AUTH-012**: System shall allow administrators to assign and modify user roles
- **REQ-AUTH-013**: System shall provide different dashboard views based on user role

### 6.2 Member Management Module

#### 6.2.1 Member Registration
- **REQ-MEM-001**: System shall allow guest users to self-register for member accounts
- **REQ-MEM-002**: System shall collect required member information: full name, email, phone, address, date of birth
- **REQ-MEM-003**: System shall validate email uniqueness across all members
- **REQ-MEM-004**: System shall generate unique member ID upon registration
- **REQ-MEM-005**: System shall set new member status to "Pending" until approved by librarian
- **REQ-MEM-006**: System shall send email verification link upon registration
- **REQ-MEM-007**: System shall allow librarians to approve or reject pending registrations

#### 6.2.2 Member Profile Management
- **REQ-MEM-008**: Members shall be able to view and update their contact information
- **REQ-MEM-009**: Members shall be able to change their password
- **REQ-MEM-010**: System shall maintain member profile history for audit purposes
- **REQ-MEM-011**: Librarians shall be able to view complete member profiles
- **REQ-MEM-012**: Librarians shall be able to update member information
- **REQ-MEM-013**: System shall display member photo/avatar if uploaded

#### 6.2.3 Member Status Management
- **REQ-MEM-014**: System shall support member statuses: Pending, Active, Suspended, Expired, Inactive
- **REQ-MEM-015**: Librarians shall be able to suspend member accounts with reason
- **REQ-MEM-016**: System shall automatically suspend members with fines exceeding threshold (e.g., $50)
- **REQ-MEM-017**: System shall automatically expire memberships after configured period (e.g., 1 year)
- **REQ-MEM-018**: System shall send notifications 30 days before membership expiration
- **REQ-MEM-019**: Members shall be able to renew expired memberships
- **REQ-MEM-020**: System shall prevent suspended members from borrowing books

### 6.3 Book Catalog Module

#### 6.3.1 Book Management
- **REQ-CAT-001**: System shall store comprehensive book information: ISBN, title, subtitle, authors, publisher, publication date, edition, language, page count, description, cover image
- **REQ-CAT-002**: System shall support multiple copies of the same book with unique copy IDs
- **REQ-CAT-003**: System shall track physical location (shelf number, section) for each book copy
- **REQ-CAT-004**: System shall support book statuses: Available, On Loan, Reserved, Processing, Damaged, Lost, Withdrawn
- **REQ-CAT-005**: Librarians shall be able to add new books to the catalog
- **REQ-CAT-006**: Librarians shall be able to edit book information
- **REQ-CAT-007**: Administrators shall be able to delete books from the catalog
- **REQ-CAT-008**: System shall prevent deletion of books with active loans or reservations
- **REQ-CAT-009**: System shall support bulk import of books via CSV or API (e.g., ISBN lookup)
- **REQ-CAT-010**: System shall maintain book condition notes and history

#### 6.3.2 Author Management
- **REQ-CAT-011**: System shall maintain author records with name, biography, and photo
- **REQ-CAT-012**: System shall support multiple authors per book
- **REQ-CAT-013**: System shall display all books by a specific author
- **REQ-CAT-014**: Librarians shall be able to add and edit author information

#### 6.3.3 Category Management
- **REQ-CAT-015**: System shall support hierarchical category structure (parent-child categories)
- **REQ-CAT-016**: System shall allow books to be assigned to multiple categories
- **REQ-CAT-017**: Administrators shall be able to create, edit, and delete categories
- **REQ-CAT-018**: System shall display book count per category

#### 6.3.4 Publisher Management
- **REQ-CAT-019**: System shall maintain publisher records with name, address, and contact information
- **REQ-CAT-020**: System shall associate books with publishers
- **REQ-CAT-021**: Librarians shall be able to add and edit publisher information

#### 6.3.5 Search & Browse
- **REQ-CAT-022**: System shall provide full-text search across title, author, ISBN, and description
- **REQ-CAT-023**: System shall support filtering by category, author, publisher, publication year, availability status
- **REQ-CAT-024**: System shall provide advanced search with multiple criteria
- **REQ-CAT-025**: System shall display search results with pagination (configurable items per page)
- **REQ-CAT-026**: System shall sort results by relevance, title, author, publication date, or popularity
- **REQ-CAT-027**: System shall provide autocomplete suggestions during search
- **REQ-CAT-028**: System shall display book availability status in search results
- **REQ-CAT-029**: Guest users shall be able to browse and search the public catalog

### 6.4 Circulation Module

#### 6.4.1 Book Checkout
- **REQ-CIR-001**: Librarians shall be able to check out books to members
- **REQ-CIR-002**: System shall verify member eligibility before checkout (active status, within borrowing limit, acceptable fine balance)
- **REQ-CIR-003**: System shall verify book availability before checkout
- **REQ-CIR-004**: System shall calculate due date based on configurable loan period (default 14 days)
- **REQ-CIR-005**: System shall create loan record with checkout date, due date, and status
- **REQ-CIR-006**: System shall update book status to "On Loan"
- **REQ-CIR-007**: System shall enforce maximum concurrent loans per member (configurable, default 5 books)
- **REQ-CIR-008**: System shall generate checkout receipt with due date
- **REQ-CIR-009**: System shall send checkout confirmation and due date reminder to member

#### 6.4.2 Book Return
- **REQ-CIR-010**: Librarians shall be able to process book returns
- **REQ-CIR-011**: System shall identify active loan by book ID
- **REQ-CIR-012**: System shall calculate if return is overdue
- **REQ-CIR-013**: System shall automatically generate fines for overdue returns
- **REQ-CIR-014**: System shall update loan record with return date and status
- **REQ-CIR-015**: System shall update book status to "Available" or "Reserved" based on reservation queue
- **REQ-CIR-016**: System shall generate return receipt
- **REQ-CIR-017**: System shall allow librarians to mark books as damaged during return
- **REQ-CIR-018**: System shall process holds/reservations automatically upon return

#### 6.4.3 Loan Renewal
- **REQ-CIR-019**: Members shall be able to renew loans online or at circulation desk
- **REQ-CIR-020**: System shall allow maximum 2 renewals per loan (configurable)
- **REQ-CIR-021**: System shall prevent renewal if book is reserved by another member
- **REQ-CIR-022**: System shall prevent renewal if loan is overdue
- **REQ-CIR-023**: System shall prevent renewal if member has excessive fines
- **REQ-CIR-024**: System shall extend due date by standard loan period upon renewal
- **REQ-CIR-025**: System shall send renewal confirmation with new due date

#### 6.4.4 Loan History
- **REQ-CIR-026**: Members shall be able to view their complete borrowing history
- **REQ-CIR-027**: Librarians shall be able to view any member's borrowing history
- **REQ-CIR-028**: System shall display loan details: book, checkout date, due date, return date, renewals, fines
- **REQ-CIR-029**: System shall allow filtering loan history by date range and status

### 6.5 Reservation Module

#### 6.5.1 Reservation Management
- **REQ-RES-001**: Members shall be able to reserve books that are currently on loan
- **REQ-RES-002**: System shall enforce maximum active reservations per member (configurable, default 5)
- **REQ-RES-003**: System shall prevent duplicate reservations by same member for same book
- **REQ-RES-004**: System shall maintain reservation queue with position tracking
- **REQ-RES-005**: System shall calculate and display estimated availability date
- **REQ-RES-006**: Members shall be able to cancel their own reservations
- **REQ-RES-007**: Librarians shall be able to cancel any reservation with reason
- **REQ-RES-008**: System shall support reservation statuses: Active, Ready for Pickup, Fulfilled, Cancelled, Expired

#### 6.5.2 Reservation Notifications
- **REQ-RES-009**: System shall notify member when reserved book becomes available
- **REQ-RES-010**: System shall set hold expiration period (configurable, default 3 days)
- **REQ-RES-011**: System shall send reminder notification 1 day before hold expiration
- **REQ-RES-012**: System shall automatically cancel reservation if not picked up by expiration date
- **REQ-RES-013**: System shall move to next member in queue when reservation expires or is cancelled

#### 6.5.3 Reservation Queue Management
- **REQ-RES-014**: System shall process reservations in first-come-first-served order
- **REQ-RES-015**: Librarians shall be able to view reservation queue for any book
- **REQ-RES-016**: System shall update queue positions automatically when reservations are fulfilled or cancelled
- **REQ-RES-017**: Members shall be able to view their position in reservation queue

### 6.6 Fine & Payment Module

#### 6.6.1 Fine Generation
- **REQ-FIN-001**: System shall automatically generate fines for overdue books
- **REQ-FIN-002**: System shall calculate fines based on configurable daily rate (default $0.50/day)
- **REQ-FIN-003**: System shall support maximum fine cap per book (configurable, default $25)
- **REQ-FIN-004**: System shall support fine types: Overdue, Damaged, Lost, Other
- **REQ-FIN-005**: Librarians shall be able to manually add fines with reason
- **REQ-FIN-006**: System shall associate fines with specific loans when applicable
- **REQ-FIN-007**: System shall send fine notification to member when generated

#### 6.6.2 Fine Management
- **REQ-FIN-008**: Members shall be able to view all outstanding and paid fines
- **REQ-FIN-009**: Librarians shall be able to view all fines for any member
- **REQ-FIN-010**: System shall display fine details: amount, reason, date assessed, status, associated loan
- **REQ-FIN-011**: Administrators shall be able to waive or reduce fines with reason
- **REQ-FIN-012**: System shall support fine statuses: Outstanding, Partially Paid, Paid, Waived
- **REQ-FIN-013**: System shall calculate total outstanding balance per member

#### 6.6.3 Payment Processing
- **REQ-FIN-014**: Librarians shall be able to process fine payments at circulation desk
- **REQ-FIN-015**: System shall support payment methods: Cash, Credit Card, Debit Card, Check, Online Payment
- **REQ-FIN-016**: System shall allow partial payments toward fines
- **REQ-FIN-017**: System shall create payment record with amount, method, date, and processing librarian
- **REQ-FIN-018**: System shall update fine status based on payment amount
- **REQ-FIN-019**: System shall generate payment receipt
- **REQ-FIN-020**: System shall send payment confirmation to member
- **REQ-FIN-021**: System shall maintain payment history for each member
- **REQ-FIN-022**: System shall support online payment integration (future enhancement)

### 6.7 Review & Rating Module

#### 6.7.1 Review Management
- **REQ-REV-001**: Members shall be able to review books they have previously borrowed
- **REQ-REV-002**: System shall allow one review per member per book
- **REQ-REV-003**: System shall support star ratings (1-5 stars) and written reviews
- **REQ-REV-004**: Members shall be able to edit or delete their own reviews
- **REQ-REV-005**: System shall display average rating and review count for each book
- **REQ-REV-006**: System shall display reviews on book detail pages
- **REQ-REV-007**: Librarians shall be able to moderate and remove inappropriate reviews
- **REQ-REV-008**: System shall timestamp all reviews

### 6.8 Notification Module

#### 6.8.1 Notification Types
- **REQ-NOT-001**: System shall send due date reminders 3 days before due date
- **REQ-NOT-002**: System shall send overdue notifications on due date and every 7 days thereafter
- **REQ-NOT-003**: System shall send reservation ready notifications when book becomes available
- **REQ-NOT-004**: System shall send reservation expiration reminders
- **REQ-NOT-005**: System shall send fine notifications when fines are assessed
- **REQ-NOT-006**: System shall send payment confirmations
- **REQ-NOT-007**: System shall send membership expiration reminders
- **REQ-NOT-008**: System shall send account suspension/reactivation notifications
- **REQ-NOT-009**: Librarians shall be able to send custom notifications to members

#### 6.8.2 Notification Delivery
- **REQ-NOT-010**: System shall support email notifications
- **REQ-NOT-011**: System shall support in-app notifications
- **REQ-NOT-012**: System shall maintain notification history for each member
- **REQ-NOT-013**: Members shall be able to view notification history
- **REQ-NOT-014**: Members shall be able to configure notification preferences
- **REQ-NOT-015**: System shall mark notifications as read/unread
- **REQ-NOT-016**: System shall retry failed email notifications up to 3 times

### 6.9 Reporting & Analytics Module

#### 6.9.1 Standard Reports
- **REQ-REP-001**: System shall generate circulation statistics report (checkouts, returns, renewals by date range)
- **REQ-REP-002**: System shall generate overdue items report with member contact information
- **REQ-REP-003**: System shall generate popular books report (most borrowed, most reserved)
- **REQ-REP-004**: System shall generate member activity report (active members, new registrations, suspensions)
- **REQ-REP-005**: System shall generate fine collection report (fines assessed, collected, outstanding)
- **REQ-REP-006**: System shall generate inventory report (total books, by category, by status)
- **REQ-REP-007**: System shall generate reservation queue report
- **REQ-REP-008**: System shall allow filtering reports by date range, category, member type

#### 6.9.2 Dashboard & Analytics
- **REQ-REP-009**: System shall provide role-specific dashboards
- **REQ-REP-010**: Librarian dashboard shall display: books due today, overdue items, pending reservations, recent activity
- **REQ-REP-011**: Member dashboard shall display: current loans with due dates, active reservations, outstanding fines, reading history
- **REQ-REP-012**: Administrator dashboard shall display: system statistics, recent member registrations, fine collection summary, popular books
- **REQ-REP-013**: System shall provide visual charts and graphs for key metrics
- **REQ-REP-014**: System shall allow exporting reports to PDF and CSV formats

### 6.10 System Administration Module

#### 6.10.1 Configuration Management
- **REQ-ADM-001**: Administrators shall be able to configure loan period (default 14 days)
- **REQ-ADM-002**: Administrators shall be able to configure maximum renewals (default 2)
- **REQ-ADM-003**: Administrators shall be able to configure maximum concurrent loans (default 5)
- **REQ-ADM-004**: Administrators shall be able to configure maximum reservations (default 5)
- **REQ-ADM-005**: Administrators shall be able to configure fine rates (daily rate, maximum cap)
- **REQ-ADM-006**: Administrators shall be able to configure reservation hold period (default 3 days)
- **REQ-ADM-007**: Administrators shall be able to configure membership duration (default 1 year)
- **REQ-ADM-008**: Administrators shall be able to configure fine threshold for suspension (default $50)
- **REQ-ADM-009**: Administrators shall be able to configure library information (name, address, contact, hours)

#### 6.10.2 User Management
- **REQ-ADM-010**: Administrators shall be able to create librarian accounts
- **REQ-ADM-011**: Administrators shall be able to deactivate user accounts
- **REQ-ADM-012**: Administrators shall be able to reset user passwords
- **REQ-ADM-013**: Administrators shall be able to view all user activity logs

#### 6.10.3 Audit & Logging
- **REQ-ADM-014**: System shall log all critical operations (checkouts, returns, payments, configuration changes)
- **REQ-ADM-015**: Audit logs shall include: timestamp, user, action, affected entity, before/after values
- **REQ-ADM-016**: Administrators shall be able to view and search audit logs
- **REQ-ADM-017**: System shall retain audit logs for minimum 2 years
- **REQ-ADM-018**: System shall prevent modification or deletion of audit logs

## 7. Business Rules

### 7.1 Member Rules
- **BR-MEM-001**: Members must be at least 13 years old to register
- **BR-MEM-002**: Each member must have a unique email address
- **BR-MEM-003**: Members with outstanding fines exceeding $50 shall be automatically suspended
- **BR-MEM-004**: Suspended members cannot borrow books or make new reservations
- **BR-MEM-005**: Memberships expire after 1 year and must be renewed
- **BR-MEM-006**: Expired memberships can be renewed within 90 days without re-registration
- **BR-MEM-007**: Members can have maximum 5 concurrent active loans
- **BR-MEM-008**: Members can have maximum 5 active reservations
- **BR-MEM-009**: Members must return all books and pay all fines before account can be closed

### 7.2 Loan Rules
- **BR-LOAN-001**: Standard loan period is 14 days from checkout date
- **BR-LOAN-002**: Loans can be renewed maximum 2 times if no reservations exist
- **BR-LOAN-003**: Each renewal extends the due date by 14 days
- **BR-LOAN-004**: Overdue loans cannot be renewed
- **BR-LOAN-005**: Books with active reservations cannot be renewed
- **BR-LOAN-006**: Members with fines exceeding $50 cannot check out new books
- **BR-LOAN-007**: Reference books and special collections may have different loan periods (configurable per book)
- **BR-LOAN-008**: A book must be returned before it can be checked out again

### 7.3 Fine Rules
- **BR-FINE-001**: Overdue fines accrue at $0.50 per day per book
- **BR-FINE-002**: Maximum fine per book is capped at $25 (replacement cost may be higher)
- **BR-FINE-003**: Fines begin accruing the day after the due date
- **BR-FINE-004**: Damaged book fines are assessed based on damage severity (minor: $5, moderate: $15, severe: replacement cost)
- **BR-FINE-005**: Lost book fines equal the replacement cost plus $10 processing fee
- **BR-FINE-006**: Fines can be waived only by administrators with documented reason
- **BR-FINE-007**: Partial payments are applied to oldest fines first
- **BR-FINE-008**: Returning a book does not waive accrued overdue fines

### 7.4 Reservation Rules
- **BR-RES-001**: Books can only be reserved if all copies are currently on loan
- **BR-RES-002**: Reservations are fulfilled in first-come-first-served order
- **BR-RES-003**: Reserved books must be picked up within 3 days of notification
- **BR-RES-004**: Expired reservations automatically move to next member in queue
- **BR-RES-005**: Members cannot reserve books they currently have on loan
- **BR-RES-006**: Suspended members cannot make new reservations but existing reservations remain active
- **BR-RES-007**: Cancelled reservations cannot be reinstated; member must create new reservation
- **BR-RES-008**: Members receive one notification when book becomes available

### 7.5 Book Rules
- **BR-BOOK-001**: Each book copy must have a unique identifier (barcode/ID)
- **BR-BOOK-002**: Books marked as "Damaged" cannot be checked out until repaired
- **BR-BOOK-003**: Books marked as "Lost" cannot be checked out and remain on member's record until resolved
- **BR-BOOK-004**: Books marked as "Withdrawn" are removed from circulation but retained in system for historical records
- **BR-BOOK-005**: ISBN must be unique per title/edition but multiple copies can share same ISBN
- **BR-BOOK-006**: Books cannot be deleted if they have active loans or reservations
- **BR-BOOK-007**: Books must be assigned to at least one category
- **BR-BOOK-008**: Book availability status is automatically managed by the system based on loans and reservations

### 7.6 Payment Rules
- **BR-PAY-001**: Payments must be applied to specific fines
- **BR-PAY-002**: Overpayments are credited to member's account for future fines
- **BR-PAY-003**: Refunds require administrator approval
- **BR-PAY-004**: Cash payments must be processed by librarians at circulation desk
- **BR-PAY-005**: All payments must be receipted
- **BR-PAY-006**: Payment records cannot be deleted, only voided with reason

### 7.7 Review Rules
- **BR-REV-001**: Members can only review books they have previously borrowed
- **BR-REV-002**: One review per member per book
- **BR-REV-003**: Reviews must include a star rating (1-5 stars)
- **BR-REV-004**: Written review text is optional but limited to 1000 characters
- **BR-REV-005**: Reviews can be edited within 30 days of posting
- **BR-REV-006**: Inappropriate reviews can be removed by librarians with documented reason

## 8. Non-Functional Requirements

### 8.1 Performance Requirements
- **NFR-PERF-001**: System shall support minimum 100 concurrent users
- **NFR-PERF-002**: Page load time shall not exceed 2 seconds under normal load
- **NFR-PERF-003**: Search queries shall return results within 1 second for catalogs up to 50,000 books
- **NFR-PERF-004**: Database queries shall be optimized with appropriate indexing
- **NFR-PERF-005**: System shall handle peak circulation periods (e.g., 50 checkouts/returns per hour)
- **NFR-PERF-006**: Report generation shall complete within 30 seconds for standard date ranges
- **NFR-PERF-007**: System shall implement caching for frequently accessed data (catalog, categories)

### 8.2 Security Requirements
- **NFR-SEC-001**: All passwords must be hashed using bcrypt or Argon2 with appropriate salt
- **NFR-SEC-002**: System shall implement HTTPS/TLS for all communications
- **NFR-SEC-003**: System shall protect against common vulnerabilities (SQL injection, XSS, CSRF)
- **NFR-SEC-004**: System shall implement rate limiting on authentication endpoints (max 5 attempts per minute)
- **NFR-SEC-005**: System shall enforce session timeout after 30 minutes of inactivity
- **NFR-SEC-006**: System shall implement role-based access control with principle of least privilege
- **NFR-SEC-007**: Sensitive data (payment information) shall be encrypted at rest
- **NFR-SEC-008**: System shall log all security-relevant events (failed logins, privilege escalation attempts)
- **NFR-SEC-009**: System shall comply with data protection regulations (GDPR, CCPA where applicable)
- **NFR-SEC-010**: System shall implement secure password reset mechanism with time-limited tokens

### 8.3 Scalability Requirements
- **NFR-SCALE-001**: System architecture shall support horizontal scaling for increased load
- **NFR-SCALE-002**: Database shall support up to 100,000 book records without performance degradation
- **NFR-SCALE-003**: System shall support up to 10,000 active member accounts
- **NFR-SCALE-004**: System shall handle up to 1,000 concurrent loans
- **NFR-SCALE-005**: File storage for book covers and documents shall be scalable (cloud storage integration)

### 8.4 Reliability & Availability Requirements
- **NFR-REL-001**: System shall have 99% uptime during library operating hours
- **NFR-REL-002**: System shall implement automated database backups daily
- **NFR-REL-003**: System shall retain backup data for minimum 30 days
- **NFR-REL-004**: System shall implement transaction rollback for failed operations
- **NFR-REL-005**: System shall gracefully handle errors with user-friendly messages
- **NFR-REL-006**: System shall log all errors with stack traces for debugging
- **NFR-REL-007**: Critical operations (checkout, return, payment) shall be atomic transactions

### 8.5 Usability Requirements
- **NFR-USE-001**: System shall provide intuitive, user-friendly interface requiring minimal training
- **NFR-USE-002**: System shall be responsive and work on desktop, tablet, and mobile devices
- **NFR-USE-003**: System shall provide clear error messages with guidance for resolution
- **NFR-USE-004**: System shall implement consistent navigation and UI patterns across all pages
- **NFR-USE-005**: System shall support keyboard navigation for accessibility
- **NFR-USE-006**: System shall meet WCAG 2.1 Level AA accessibility standards
- **NFR-USE-007**: System shall provide contextual help and tooltips for complex features
- **NFR-USE-008**: System shall support multiple languages (English as default, extensible for others)

### 8.6 Maintainability Requirements
- **NFR-MAINT-001**: Code shall follow established coding standards and best practices
- **NFR-MAINT-002**: System shall be modular with clear separation of concerns
- **NFR-MAINT-003**: System shall include comprehensive API documentation
- **NFR-MAINT-004**: System shall include unit tests with minimum 70% code coverage
- **NFR-MAINT-005**: System shall use version control (Git) for all code
- **NFR-MAINT-006**: Database schema changes shall be managed through migrations
- **NFR-MAINT-007**: System shall implement logging at appropriate levels (DEBUG, INFO, WARN, ERROR)

### 8.7 Compatibility Requirements
- **NFR-COMP-001**: System shall support modern web browsers (Chrome, Firefox, Safari, Edge - latest 2 versions)
- **NFR-COMP-002**: System shall be compatible with mobile browsers (iOS Safari, Chrome Mobile)
- **NFR-COMP-003**: System shall support barcode scanner integration for book and member ID scanning
- **NFR-COMP-004**: System shall provide REST API for potential third-party integrations
- **NFR-COMP-005**: System shall support standard data export formats (CSV, PDF, JSON)

### 8.8 Data Requirements
- **NFR-DATA-001**: System shall validate all input data before processing
- **NFR-DATA-002**: System shall sanitize user input to prevent injection attacks
- **NFR-DATA-003**: System shall maintain referential integrity in database
- **NFR-DATA-004**: System shall implement soft deletes for critical entities (retain data with deleted flag)
- **NFR-DATA-005**: System shall archive old data (loans older than 5 years) to maintain performance
- **NFR-DATA-006**: System shall provide data export functionality for member data requests (GDPR compliance)

### 8.9 Notification Requirements
- **NFR-NOTIF-001**: Email notifications shall be queued and processed asynchronously
- **NFR-NOTIF-002**: System shall retry failed email deliveries up to 3 times with exponential backoff
- **NFR-NOTIF-003**: System shall log all notification attempts and delivery status
- **NFR-NOTIF-004**: Email templates shall be configurable by administrators
- **NFR-NOTIF-005**: System shall respect member notification preferences (opt-out options)

### 8.10 Deployment Requirements
- **NFR-DEPLOY-001**: System shall be containerized (Docker) for consistent deployment
- **NFR-DEPLOY-002**: System shall include deployment documentation and scripts
- **NFR-DEPLOY-003**: System shall support environment-specific configuration (development, staging, production)
- **NFR-DEPLOY-004**: System shall implement database migration strategy for version updates
- **NFR-DEPLOY-005**: System shall include health check endpoints for monitoring

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**Document Version**: 1.0  
**Last Updated**: 2025  
**Author**: Senior Product Manager  
**Status**: Ready for Development