# Product Requirements Document: Library Management System

## 1. Overview

The Library Management System is a comprehensive digital platform designed to automate and streamline the operations of a library, including catalog management, member registration, book lending and returns, reservations, and fine collection. The system enables librarians to efficiently manage library resources while providing members with self-service capabilities to search, borrow, and reserve books. This application aims to replace manual record-keeping with a robust, user-friendly digital solution that improves operational efficiency and enhances the user experience for both library staff and patrons.

## 2. User Roles

### 2.1 Guest (Unauthenticated User)
- Browse the public catalog of books
- Search for books by title, author, ISBN, or category
- View book details and availability status
- View library information and policies

### 2.2 Member (Authenticated Library Patron)
- All Guest capabilities
- Register for a library membership
- Borrow books (check out)
- Return books
- Reserve books that are currently checked out
- View personal borrowing history
- View current checked-out books
- View and pay outstanding fines
- Update personal profile information
- Renew borrowed books (if eligible)

### 2.3 Librarian (Staff Member)
- All Member capabilities
- Add, edit, and remove books from the catalog
- Add, edit, and deactivate member accounts
- Check out books on behalf of members
- Check in returned books
- Process book reservations
- Calculate and apply fines for overdue books
- Process fine payments
- Generate reports on library operations
- Manage book categories and authors
- View system-wide borrowing statistics

### 2.4 Administrator (System Admin)
- All Librarian capabilities
- Manage user roles and permissions
- Add, edit, and remove librarian accounts
- Configure system settings (loan periods, fine rates, reservation limits)
- Access audit logs
- Manage library branches (if multi-branch)
- Backup and restore system data
- View comprehensive analytics and dashboards

## 3. Core Entities

### 3.1 User
Base entity representing any person in the system with authentication credentials and role-based permissions.

### 3.2 Member
A library patron who can borrow books; extends User with membership-specific information including membership number, join date, membership status, and contact details.

### 3.3 Librarian
A staff member who manages library operations; extends User with employee-specific information including employee ID, hire date, and assigned branch.

### 3.4 Administrator
A system administrator with full access; extends User with admin-specific permissions and audit capabilities.

### 3.5 Book
A physical item in the library's collection with details including ISBN, title, publisher, publication date, edition, number of pages, language, and physical location.

### 3.6 Author
A person who has written one or more books, with details including name, biography, birth date, and nationality.

### 3.7 Category
A classification or genre used to organize books (e.g., Fiction, Science, History, Biography).

### 3.8 BookCopy
A physical copy of a book; multiple copies of the same book can exist, each with a unique barcode, condition status, and availability status.

### 3.9 Loan
A transaction representing a book being borrowed by a member, including checkout date, due date, return date, renewal count, and associated member and book copy.

### 3.10 Reservation
A request by a member to borrow a book that is currently unavailable, including reservation date, expiration date, status, and priority in the queue.

### 3.11 Fine
A monetary penalty assessed to a member for overdue books or damaged items, including amount, reason, issue date, payment status, and payment date.

### 3.12 Payment
A transaction recording a member's payment toward fines, including amount, payment method, transaction date, and reference number.

### 3.13 LibraryBranch
A physical library location with details including name, address, contact information, and operating hours.

### 3.14 AuditLog
A record of significant system actions for security and compliance, including user, action type, timestamp, entity affected, and details.

### 3.15 SystemConfiguration
Global settings for the library system including loan duration, maximum renewals, fine rates, reservation limits, and grace periods.

## 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 → BookCopy**: One-to-many (one book can have multiple physical copies)

### 4.3 BookCopy Relationships
- **BookCopy → Loan**: One-to-many (one copy can be loaned multiple times over its lifetime)
- **BookCopy → LibraryBranch**: Many-to-one (many copies belong to one branch)

### 4.4 Member Relationships
- **Member → Loan**: One-to-many (one member can have multiple loans)
- **Member → Reservation**: One-to-many (one member can have multiple reservations)
- **Member → Fine**: One-to-many (one member can have multiple fines)
- **Member → Payment**: One-to-many (one member can make multiple payments)
- **Member → LibraryBranch**: Many-to-one (many members belong to one home branch)

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

### 4.6 Reservation Relationships
- **Reservation → Member**: Many-to-one (many reservations belong to one member)
- **Reservation → Book**: Many-to-one (many reservations for one book)

### 4.7 Fine Relationships
- **Fine → Member**: Many-to-one (many fines belong to one member)
- **Fine → Loan**: Many-to-one (many fines can be associated with one loan)
- **Fine → Payment**: Many-to-many (a fine can be partially paid by multiple payments; a payment can cover multiple fines)

### 4.8 Librarian Relationships
- **Librarian → LibraryBranch**: Many-to-one (many librarians work at one branch)
- **Librarian → Loan**: One-to-many (one librarian processes many loans)

## 5. Key Workflows

### 5.1 Member Registration Workflow
1. Guest navigates to registration page
2. Guest fills out registration form (name, email, phone, address, date of birth)
3. System validates input data (email format, required fields, age requirements)
4. System checks for duplicate email/phone
5. System generates unique membership number
6. System creates Member account with "Pending" status
7. Librarian reviews and approves membership
8. System updates status to "Active"
9. System sends welcome email with membership details
10. Member can now log in and use library services

### 5.2 Book Checkout Workflow
1. Member or Librarian initiates checkout process
2. System scans or enters book copy barcode
3. System verifies book copy is available (status = "Available")
4. System verifies member eligibility:
   - Membership status is "Active"
   - No outstanding fines exceeding limit
   - Current loan count below maximum allowed
5. System creates Loan record with:
   - Checkout date = current date
   - Due date = current date + loan period (from SystemConfiguration)
   - Status = "Active"
6. System updates BookCopy status to "Checked Out"
7. System checks for any reservations for this book
8. If reservations exist, system notifies next member in queue
9. System sends confirmation email/receipt to member
10. System displays due date and return instructions

### 5.3 Book Return Workflow
1. Member returns book to library or Librarian scans returned book
2. System retrieves active Loan record for the book copy
3. System sets return date = current date
4. System calculates if book is overdue (return date > due date)
5. If overdue:
   - System calculates fine amount (days overdue × daily fine rate)
   - System creates Fine record linked to Loan and Member
   - System notifies member of fine
6. System updates Loan status to "Returned"
7. System inspects book condition (Librarian input)
8. If damaged:
   - System creates additional Fine for damage
9. System updates BookCopy status to "Available"
10. System checks for active Reservations for this book
11. If reservation exists:
    - System updates BookCopy status to "Reserved"
    - System notifies member that book is ready for pickup
    - System sets reservation expiration (e.g., 48 hours)
12. System sends return confirmation to member

### 5.4 Book Reservation Workflow
1. Member searches for and selects a book
2. System checks if any copies are available
3. If all copies are checked out, member clicks "Reserve"
4. System verifies member eligibility:
   - Active membership
   - Current reservation count below maximum
5. System creates Reservation record with:
   - Reservation date = current date
   - Status = "Pending"
   - Priority = next in queue
6. System sends confirmation to member with queue position
7. When book becomes available:
   - System updates Reservation status to "Ready"
   - System updates BookCopy status to "Reserved"
   - System sends notification to member
   - System sets expiration date (e.g., 48 hours from notification)
8. Member picks up book within expiration period:
   - System converts Reservation to Loan
   - System follows checkout workflow
9. If member doesn't pick up within expiration:
   - System cancels Reservation
   - System moves to next member in queue
   - System updates BookCopy status to "Available"

### 5.5 Book Renewal Workflow
1. Member requests renewal for a checked-out book
2. System retrieves active Loan record
3. System verifies renewal eligibility:
   - Loan is not overdue
   - Renewal count < maximum renewals allowed
   - No active reservations for this book
   - Member has no excessive outstanding fines
4. If eligible:
   - System increments renewal count
   - System extends due date by loan period
   - System updates Loan record
   - System sends confirmation with new due date
5. If not eligible:
   - System displays reason for denial
   - System suggests returning book or contacting librarian

### 5.6 Fine Payment Workflow
1. Member views outstanding fines in their account
2. Member selects fines to pay
3. System calculates total amount due
4. Member selects payment method (cash, card, online)
5. System processes payment:
   - For online: integrates with payment gateway
   - For in-person: Librarian confirms receipt
6. System creates Payment record
7. System updates Fine records:
   - If full payment: status = "Paid", payment date = current date
   - If partial payment: reduces amount, status remains "Unpaid"
8. System generates receipt
9. System sends payment confirmation email
10. If all fines paid, system removes any borrowing restrictions

### 5.7 Overdue Book Management Workflow
1. System runs daily automated job to check for overdue books
2. System queries all Loans where due date < current date AND status = "Active"
3. For each overdue loan:
   - System calculates days overdue
   - System checks if Fine already exists for this loan
   - If no Fine exists, system creates Fine record
   - If Fine exists, system updates amount (days overdue × daily rate)
4. System sends overdue notification to member (email/SMS)
5. If overdue > grace period:
   - System sends escalated reminder
6. If overdue > suspension threshold:
   - System updates Member status to "Suspended"
   - System prevents new checkouts
7. System generates overdue report for librarians
8. Librarian can take additional actions (phone calls, collection notices)

## 6. Features & Requirements

### 6.1 Authentication & Authorization Module

#### 6.1.1 User Registration
- **FR-AUTH-001**: System shall allow guests to register for a member account
- **FR-AUTH-002**: System shall require email, password, full name, phone number, and address during registration
- **FR-AUTH-003**: System shall validate email format and uniqueness
- **FR-AUTH-004**: System shall enforce password complexity requirements (minimum 8 characters, uppercase, lowercase, number)
- **FR-AUTH-005**: System shall generate unique membership numbers automatically
- **FR-AUTH-006**: System shall send verification email upon registration

#### 6.1.2 Login & Session Management
- **FR-AUTH-007**: System shall allow users to log in with email and password
- **FR-AUTH-008**: System shall implement session timeout after 30 minutes of inactivity
- **FR-AUTH-009**: System shall allow users to log out manually
- **FR-AUTH-010**: System shall lock accounts after 5 failed login attempts
- **FR-AUTH-011**: System shall provide "Forgot Password" functionality with email reset link

#### 6.1.3 Role-Based Access Control
- **FR-AUTH-012**: System shall enforce role-based permissions for all operations
- **FR-AUTH-013**: System shall restrict administrative functions to Administrator role only
- **FR-AUTH-014**: System shall allow Librarians to perform member management and circulation tasks
- **FR-AUTH-015**: System shall restrict Members to self-service operations only

### 6.2 Catalog Management Module

#### 6.2.1 Book Management
- **FR-CAT-001**: System shall allow Librarians to add new books with ISBN, title, authors, publisher, publication date, edition, pages, language, and description
- **FR-CAT-002**: System shall validate ISBN format (ISBN-10 or ISBN-13)
- **FR-CAT-003**: System shall allow Librarians to edit book information
- **FR-CAT-004**: System shall allow Librarians to soft-delete books (mark as inactive rather than permanent deletion)
- **FR-CAT-005**: System shall support uploading book cover images
- **FR-CAT-006**: System shall allow associating multiple authors with a book
- **FR-CAT-007**: System shall allow associating multiple categories with a book

#### 6.2.2 Book Copy Management
- **FR-CAT-008**: System shall allow Librarians to add multiple copies of the same book
- **FR-CAT-009**: System shall generate unique barcodes for each book copy
- **FR-CAT-010**: System shall track condition status for each copy (New, Good, Fair, Poor, Damaged)
- **FR-CAT-011**: System shall track availability status for each copy (Available, Checked Out, Reserved, In Repair, Lost)
- **FR-CAT-012**: System shall allow Librarians to update copy condition and status
- **FR-CAT-013**: System shall assign each copy to a library branch

#### 6.2.3 Author Management
- **FR-CAT-014**: System shall allow Librarians to add new authors with name, biography, birth date, and nationality
- **FR-CAT-015**: System shall allow Librarians to edit author information
- **FR-CAT-016**: System shall display all books by a specific author

#### 6.2.4 Category Management
- **FR-CAT-017**: System shall allow Librarians to create new categories
- **FR-CAT-018**: System shall allow Librarians to edit and delete categories
- **FR-CAT-019**: System shall support hierarchical categories (parent-child relationships)
- **FR-CAT-020**: System shall display all books in a specific category

### 6.3 Search & Discovery Module

#### 6.3.1 Book Search
- **FR-SEARCH-001**: System shall allow users to search books by title (partial match)
- **FR-SEARCH-002**: System shall allow users to search books by author name
- **FR-SEARCH-003**: System shall allow users to search books by ISBN
- **FR-SEARCH-004**: System shall allow users to search books by category
- **FR-SEARCH-005**: System shall allow users to search books by keyword (searches title, description, author)
- **FR-SEARCH-006**: System shall support advanced search with multiple filters (author, category, publication year, language)
- **FR-SEARCH-007**: System shall display search results with pagination (20 results per page)
- **FR-SEARCH-008**: System shall allow sorting results by title, author, publication date, or relevance

#### 6.3.2 Book Details & Availability
- **FR-SEARCH-009**: System shall display comprehensive book details including all metadata
- **FR-SEARCH-010**: System shall display total number of copies and available copies
- **FR-SEARCH-011**: System shall display expected return dates for checked-out copies
- **FR-SEARCH-012**: System shall display number of active reservations
- **FR-SEARCH-013**: System shall show book location (branch and shelf number)

#### 6.3.3 Browse & Recommendations
- **FR-SEARCH-014**: System shall allow users to browse books by category
- **FR-SEARCH-015**: System shall display "New Arrivals" (books added in last 30 days)
- **FR-SEARCH-016**: System shall display "Popular Books" (most borrowed in last 90 days)
- **FR-SEARCH-017**: System shall display "Recommended for You" based on borrowing history (for logged-in members)

### 6.4 Circulation Module

#### 6.4.1 Checkout Operations
- **FR-CIRC-001**: System shall allow Librarians to check out books by scanning barcode
- **FR-CIRC-002**: System shall allow Members to initiate self-checkout (if enabled)
- **FR-CIRC-003**: System shall verify book availability before checkout
- **FR-CIRC-004**: System shall verify member eligibility before checkout
- **FR-CIRC-005**: System shall enforce maximum concurrent loans per member (configurable, default 5)
- **FR-CIRC-006**: System shall prevent checkout if member has fines exceeding threshold (configurable, default $10)
- **FR-CIRC-007**: System shall calculate due date based on loan period configuration
- **FR-CIRC-008**: System shall generate checkout receipt with due date
- **FR-CIRC-009**: System shall send checkout confirmation email to member

#### 6.4.2 Return Operations
- **FR-CIRC-010**: System shall allow Librarians to check in books by scanning barcode
- **FR-CIRC-011**: System shall calculate and display overdue days if applicable
- **FR-CIRC-012**: System shall automatically create fine for overdue returns
- **FR-CIRC-013**: System shall allow Librarians to assess condition and create damage fines
- **FR-CIRC-014**: System shall update book availability immediately upon return
- **FR-CIRC-015**: System shall trigger reservation notification if book is reserved
- **FR-CIRC-016**: System shall generate return receipt
- **FR-CIRC-017**: System shall send return confirmation email to member

#### 6.4.3 Renewal Operations
- **FR-CIRC-018**: System shall allow Members to renew books online
- **FR-CIRC-019**: System shall allow Librarians to renew books on behalf of members
- **FR-CIRC-020**: System shall enforce maximum renewal limit (configurable, default 2)
- **FR-CIRC-021**: System shall prevent renewal if book is reserved by another member
- **FR-CIRC-022**: System shall prevent renewal if book is overdue
- **FR-CIRC-023**: System shall extend due date by standard loan period upon renewal
- **FR-CIRC-024**: System shall send renewal confirmation with new due date

### 6.5 Reservation Module

#### 6.5.1 Reservation Creation
- **FR-RES-001**: System shall allow Members to reserve books that are currently unavailable
- **FR-RES-002**: System shall enforce maximum concurrent reservations per member (configurable, default 3)
- **FR-RES-003**: System shall assign queue position based on reservation timestamp
- **FR-RES-004**: System shall display estimated wait time based on loan period and queue position
- **FR-RES-005**: System shall prevent reservations if member has suspended status

#### 6.5.2 Reservation Management
- **FR-RES-006**: System shall allow Members to view their active reservations
- **FR-RES-007**: System shall allow Members to cancel reservations
- **FR-RES-008**: System shall automatically notify member when reserved book becomes available
- **FR-RES-009**: System shall set pickup expiration period (configurable, default 48 hours)
- **FR-RES-010**: System shall automatically cancel reservation if not picked up within expiration period
- **FR-RES-011**: System shall move to next member in queue when reservation expires or is cancelled
- **FR-RES-012**: System shall allow Librarians to manually fulfill reservations
- **FR-RES-013**: System shall convert reservation to loan when book is checked out

### 6.6 Fine & Payment Module

#### 6.6.1 Fine Calculation & Management
- **FR-FINE-001**: System shall automatically calculate overdue fines based on daily rate (configurable, default $0.50/day)
- **FR-FINE-002**: System shall support maximum fine cap per item (configurable, default $10)
- **FR-FINE-003**: System shall allow Librarians to manually create fines (e.g., for damage, lost books)
- **FR-FINE-004**: System shall support different fine types (Overdue, Damage, Lost Book, Other)
- **FR-FINE-005**: System shall allow Librarians to waive or reduce fines with reason
- **FR-FINE-006**: System shall display all outstanding fines to members
- **FR-FINE-007**: System shall calculate total outstanding balance per member
- **FR-FINE-008**: System shall send fine notifications via email

#### 6.6.2 Payment Processing
- **FR-FINE-009**: System shall allow Members to view payment history
- **FR-FINE-010**: System shall allow Librarians to record cash payments
- **FR-FINE-011**: System shall allow Librarians to record card payments
- **FR-FINE-012**: System shall integrate with payment gateway for online payments
- **FR-FINE-013**: System shall support partial payments
- **FR-FINE-014**: System shall generate payment receipts with transaction ID
- **FR-FINE-015**: System shall send payment confirmation email
- **FR-FINE-016**: System shall update member borrowing privileges immediately upon payment

### 6.7 Member Management Module

#### 6.7.1 Member Profile
- **FR-MEM-001**: System shall allow Members to view their profile information
- **FR-MEM-002**: System shall allow Members to update contact information (email, phone, address)
- **FR-MEM-003**: System shall allow Members to change password
- **FR-MEM-004**: System shall display membership number, join date, and status
- **FR-MEM-005**: System shall display current borrowing statistics (active loans, reservations, fines)

#### 6.7.2 Member Administration
- **FR-MEM-006**: System shall allow Librarians to search members by name, email, phone, or membership number
- **FR-MEM-007**: System shall allow Librarians to view complete member details
- **FR-MEM-008**: System shall allow Librarians to edit member information
- **FR-MEM-009**: System shall allow Librarians to update membership status (Active, Suspended, Expired, Cancelled)
- **FR-MEM-010**: System shall allow Librarians to view member borrowing history
- **FR-MEM-011**: System shall allow Librarians to view member fine history
- **FR-MEM-012**: System shall display member activity timeline

#### 6.7.3 Member Dashboard
- **FR-MEM-013**: System shall display dashboard with current checked-out books
- **FR-MEM-014**: System shall display upcoming due dates with visual indicators
- **FR-MEM-015**: System shall display active reservations with queue position
- **FR-MEM-016**: System shall display outstanding fines with payment option
- **FR-MEM-017**: System shall display borrowing history with filters
- **FR-MEM-018**: System shall allow quick renewal from dashboard

### 6.8 Reporting & Analytics Module

#### 6.8.1 Circulation Reports
- **FR-REP-001**: System shall generate daily circulation report (checkouts, returns, renewals)
- **FR-REP-002**: System shall generate overdue books report with member contact information
- **FR-REP-003**: System shall generate most borrowed books report (by period)
- **FR-REP-004**: System shall generate least borrowed books report (to identify candidates for removal)
- **FR-REP-005**: System shall generate member activity report (active vs. inactive members)

#### 6.8.2 Financial Reports
- **FR-REP-006**: System shall generate fine collection report (by period)
- **FR-REP-007**: System shall generate outstanding fines report
- **FR-REP-008**: System shall generate payment transaction report
- **FR-REP-009**: System shall generate revenue summary report

#### 6.8.3 Inventory Reports
- **FR-REP-010**: System shall generate catalog inventory report (total books, copies, by category)
- **FR-REP-011**: System shall generate book condition report
- **FR-REP-012**: System shall generate missing/lost books report
- **FR-REP-013**: System shall generate new acquisitions report

#### 6.8.4 Analytics Dashboard
- **FR-REP-014**: System shall display real-time statistics (books checked out today, returns, new members)
- **FR-REP-015**: System shall display circulation trends (charts for daily/weekly/monthly activity)
- **FR-REP-016**: System shall display popular categories and authors
- **FR-REP-017**: System shall display member demographics and statistics
- **FR-REP-018**: System shall allow exporting reports to PDF and Excel formats

### 6.9 System Administration Module

#### 6.9.1 User Management
- **FR-ADMIN-001**: System shall allow Administrators to create Librarian accounts
- **FR-ADMIN-002**: System shall allow Administrators to edit user roles
- **FR-ADMIN-003**: System shall allow Administrators to deactivate user accounts
- **FR-ADMIN-004**: System shall allow Administrators to reset user passwords
- **FR-ADMIN-005**: System shall display all users with filtering by role and status

#### 6.9.2 System Configuration
- **FR-ADMIN-006**: System shall allow Administrators to configure loan period (default 14 days)
- **FR-ADMIN-007**: System shall allow Administrators to configure maximum renewals (default 2)
- **FR-ADMIN-008**: System shall allow Administrators to configure maximum concurrent loans (default 5)
- **FR-ADMIN-009**: System shall allow Administrators to configure maximum reservations (default 3)
- **FR-ADMIN-010**: System shall allow Administrators to configure overdue fine rate (default $0.50/day)
- **FR-ADMIN-011**: System shall allow Administrators to configure maximum fine per item (default $10)
- **FR-ADMIN-012**: System shall allow Administrators to configure fine threshold for borrowing suspension (default $10)
- **FR-ADMIN-013**: System shall allow Administrators to configure reservation pickup expiration (default 48 hours)
- **FR-ADMIN-014**: System shall allow Administrators to configure grace period for overdue notifications (default 1 day)

#### 6.9.3 Branch Management
- **FR-ADMIN-015**: System shall allow Administrators to add library branches
- **FR-ADMIN-016**: System shall allow Administrators to edit branch information (name, address, hours)
- **FR-ADMIN-017**: System shall allow Administrators to assign librarians to branches
- **FR-ADMIN-018**: System shall allow Administrators to deactivate branches

#### 6.9.4 Audit & Logging
- **FR-ADMIN-019**: System shall log all significant actions (user login, book checkout, fine creation, configuration changes)
- **FR-ADMIN-020**: System shall allow Administrators to view audit logs with filtering
- **FR-ADMIN-021**: System shall record user, timestamp, action type, and affected entity for each log entry
- **FR-ADMIN-022**: System shall retain audit logs for minimum 1 year

### 6.10 Notification Module

#### 6.10.1 Email Notifications
- **FR-NOTIF-001**: System shall send welcome email upon member registration
- **FR-NOTIF-002**: System shall send checkout confirmation with due date
- **FR-NOTIF-003**: System shall send return confirmation
- **FR-NOTIF-004**: System shall send renewal confirmation with new due date
- **FR-NOTIF-005**: System shall send reservation confirmation with queue position
- **FR-NOTIF-006**: System shall send notification when reserved book is available
- **FR-NOTIF-007**: System shall send overdue reminder (1 day after due date)
- **FR-NOTIF-008**: System shall send escalated overdue notice (7 days after due date)
- **FR-NOTIF-009**: System shall send fine notification when fine is assessed
- **FR-NOTIF-010**: System shall send payment confirmation receipt
- **FR-NOTIF-011**: System shall send due date reminder (2 days before due date)

#### 6.10.2 In-App Notifications
- **FR-NOTIF-012**: System shall display in-app notifications for important events
- **FR-NOTIF-013**: System shall allow users to mark notifications as read
- **FR-NOTIF-014**: System shall display notification count badge
- **FR-NOTIF-015**: System shall retain notifications for 30 days

## 7. Business Rules

### 7.1 Membership 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**: Membership expires after 1 year of inactivity (no loans or logins)
- **BR-MEM-004**: Suspended members cannot check out or reserve books but can return books and pay fines
- **BR-MEM-005**: Members with outstanding fines exceeding $10 cannot check out or reserve books
- **BR-MEM-006**: Cancelled memberships cannot be reactivated; member must register again

### 7.2 Circulation Rules
- **BR-CIRC-001**: A member can have maximum 5 concurrent active loans
- **BR-CIRC-002**: Standard loan period is 14 days
- **BR-CIRC-003**: A book can be renewed maximum 2 times
- **BR-CIRC-004**: A book cannot be renewed if it is reserved by another member
- **BR-CIRC-005**: A book cannot be renewed if it is overdue
- **BR-CIRC-006**: Books must be returned to any library branch (not necessarily the checkout branch)
- **BR-CIRC-007**: Reference books and special collections cannot be checked out (marked as "Reference Only")
- **BR-CIRC-008**: New releases may have shorter loan periods (7 days) and no renewals

### 7.3 Reservation Rules
- **BR-RES-001**: A member can have maximum 3 concurrent active reservations
- **BR-RES-002**: Reservations are fulfilled in first-come, first-served order (by timestamp)
- **BR-RES-003**: Reserved books must be picked up within 48 hours of notification
- **BR-RES-004**: If not picked up within 48 hours, reservation is automatically cancelled
- **BR-RES-005**: Members cannot reserve books they currently have checked out
- **BR-RES-006**: Members cannot reserve the same book multiple times simultaneously
- **BR-RES-007**: Reservations automatically expire after 90 days if never fulfilled

### 7.4 Fine Rules
- **BR-FINE-001**: Overdue fine rate is $0.50 per day per book
- **BR-FINE-002**: Maximum overdue fine per book is $10 (replacement cost threshold)
- **BR-FINE-003**: Grace period of 1 day before overdue fines start accruing
- **BR-FINE-004**: Lost book fine equals replacement cost plus $5 processing fee
- **BR-FINE-005**: Damaged book fine ranges from $5 to full replacement cost based on damage severity
- **BR-FINE-006**: Fines must be paid before membership can be renewed
- **BR-FINE-007**: Partial payments are accepted and credited to oldest fines first
- **BR-FINE-008**: Fines older than 2 years may be written off by Administrator

### 7.5 Book Copy Rules
- **BR-COPY-001**: Each book copy must have a unique barcode
- **BR-COPY-002**: Book copies marked as "Lost" cannot be checked out
- **BR-COPY-003**: Book copies marked as "In Repair" cannot be checked out or reserved
- **BR-COPY-004**: Book copies in "Poor" or "Damaged" condition should be flagged for review
- **BR-COPY-005**: When all copies of a book are unavailable, the book should show "Available for Reservation"
- **BR-COPY-006**: Book copies cannot be deleted if they have active loans or reservations

### 7.6 Data Integrity Rules
- **BR-DATA-001**: Books cannot be deleted if they have book copies
- **BR-DATA-002**: Book copies cannot be deleted if they have loan history (soft delete only)
- **BR-DATA-003**: Members cannot be deleted if they have outstanding loans or fines (deactivate only)
- **BR-DATA-004**: Authors cannot be deleted if they are associated with books
- **BR-DATA-005**: Categories cannot be deleted if they contain books
- **BR-DATA-006**: Loan records must be retained permanently for historical reporting
- **BR-DATA-007**: Payment records must be retained permanently for financial auditing

### 7.7 Security Rules
- **BR-SEC-001**: Passwords must be hashed using bcrypt or similar strong algorithm
- **BR-SEC-002**: Sessions must expire after 30 minutes of inactivity
- **BR-SEC-003**: Failed login attempts must be logged
- **BR-SEC-004**: Accounts must be locked after 5 consecutive failed login attempts
- **BR-SEC-005**: Password reset links must expire after 1 hour
- **BR-SEC-006**: Users can only view and modify their own data (except Librarians and Administrators)
- **BR-SEC-007**: All financial transactions must be logged in audit trail

## 8. Non-Functional Requirements

### 8.1 Performance Requirements
- **NFR-PERF-001**: System shall load search results within 2 seconds for queries returning up to 1000 results
- **NFR-PERF-002**: System shall complete checkout/return operations within 1 second
- **NFR-PERF-003**: System shall support at least 100 concurrent users without performance degradation
- **NFR-PERF-004**: Database queries shall be optimized with appropriate indexes on frequently searched fields
- **NFR-PERF-005**: System shall implement pagination for all list views to limit data transfer
- **NFR-PERF-006**: System shall cache frequently accessed data (categories, system configuration)
- **NFR-PERF-007**: System shall generate reports asynchronously for large datasets (>10,000 records)

### 8.2 Scalability Requirements
- **NFR-SCALE-001**: System architecture shall support horizontal scaling for increased load
- **NFR-SCALE-002**: Database shall support at least 100,000 book records
- **NFR-SCALE-003**: Database shall support at least 50,000 member records
- **NFR-SCALE-004**: System shall support at least 10 library branches
- **NFR-SCALE-005**: System shall handle at least 1,000 transactions (checkouts/returns) per day

### 8.3 Security Requirements
- **NFR-SEC-001**: System shall use HTTPS for all communications
- **NFR-SEC-002**: System shall implement role-based access control (RBAC) for all operations
- **NFR-SEC-003**: System shall hash passwords using bcrypt with minimum cost factor of 10
- **NFR-SEC-004**: System shall protect against SQL injection through parameterized queries or ORM
- **NFR-SEC-005**: System shall protect against Cross-Site Scripting (XSS) through input sanitization
- **NFR-SEC-006**: System shall protect against Cross-Site Request Forgery (CSRF) using tokens
- **NFR-SEC-007**: System shall implement rate limiting to prevent brute force attacks
- **NFR-SEC-008**: System shall log all authentication attempts and security-relevant events
- **NFR-SEC-009**: System shall encrypt sensitive data at rest (passwords, payment information)
- **NFR-SEC-010**: System shall comply with data privacy regulations (GDPR, CCPA where applicable)

### 8.4 Reliability & Availability Requirements
- **NFR-REL-001**: System shall have 99% uptime during operating hours (excluding planned maintenance)
- **NFR-REL-002**: System shall implement automated database backups daily
- **NFR-REL-003**: System shall retain backups for minimum 30 days
- **NFR-REL-004**: System shall implement transaction rollback for failed operations
- **NFR-REL-005**: System shall gracefully handle errors and display user-friendly error messages
- **NFR-REL-006**: System shall log all errors with stack traces for debugging
- **NFR-REL-007**: System shall implement health check endpoints for monitoring

### 8.5 Usability Requirements
- **NFR-USE-001**: System shall provide responsive design supporting desktop, tablet, and mobile devices
- **NFR-USE-002**: System shall follow WCAG 2.1 Level AA accessibility guidelines
- **NFR-USE-003**: System shall provide clear error messages with guidance on resolution
- **NFR-USE-004**: System shall provide inline validation for form inputs
- **NFR-USE-005**: System shall use consistent UI patterns and navigation throughout
- **NFR-USE-006**: System shall provide help documentation and tooltips for complex features
- **NFR-USE-007**: System shall support keyboard navigation for all interactive elements
- **NFR-USE-008**: System shall provide visual feedback for all user actions (loading indicators, success messages)

### 8.6 Maintainability Requirements
- **NFR-MAINT-001**: Code shall follow consistent style guidelines and naming conventions
- **NFR-MAINT-002**: System shall implement comprehensive error logging
- **NFR-MAINT-003**: System shall use environment-based configuration (development, staging, production)
- **NFR-MAINT-004**: System shall include API documentation (e.g., Swagger/OpenAPI)
- **NFR-MAINT-005**: System shall implement automated testing (unit tests, integration tests)
- **NFR-MAINT-006**: System shall achieve minimum 70% code coverage with tests
- **NFR-MAINT-007**: System shall use version control (Git) with clear commit messages

### 8.7 Compatibility Requirements
- **NFR-COMP-001**: System shall support modern browsers (Chrome, Firefox, Safari, Edge - latest 2 versions)
- **NFR-COMP-002**: System shall support barcode scanners via USB or Bluetooth
- **NFR-COMP-003**: System shall provide REST API for potential third-party integrations
- **NFR-COMP-004**: System shall support standard date/time formats (ISO 8601)
- **NFR-COMP-005**: System shall support internationalization (i18n) framework for future localization

### 8.8 Data Requirements
- **NFR-DATA-001**: System shall validate all input data before processing
- **NFR-DATA-002**: System shall sanitize all user-generated content before storage and display
- **NFR-DATA-003**: System shall implement soft deletes for critical entities (members, books, loans)
- **NFR-DATA-004**: System shall maintain referential integrity through foreign key constraints
- **NFR-DATA-005**: System shall implement database migrations for schema changes
- **NFR-DATA-006**: System shall archive old data (loans older than 5 years) to separate tables for performance

### 8.9 Monitoring & Observability Requirements
- **NFR-MON-001**: System shall implement application performance monitoring (APM)
- **NFR-MON-002**: System shall track key metrics (response times, error rates, active users)
- **NFR-MON-003**: System shall implement alerting for critical errors and system issues
- **NFR-MON-004**: System shall provide admin dashboard with system health indicators
- **NFR-MON-005**: System shall log all API requests with response times

### 8.10 Compliance Requirements
- **NFR-COMP-001**: System shall comply with data protection regulations for user data
- **NFR-COMP-002**: System shall provide data export functionality for user data portability
- **NFR-COMP-003**: System shall provide data deletion functionality for "right to be forgotten"
- **NFR-COMP-004**: System shall maintain audit trails for compliance reporting
- **NFR-COMP-005**: System shall implement data retention policies per legal requirements

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