Object-Oriented Design for a Library Management System
Problem
Design an Object-Oriented Library Management System to manage books, copies (book items), members, checkouts, reservations, renewals, fines, and notifications. The system should support searching the catalog, issuing and returning book items, reserving unavailable copies, enforcing borrowing limits and due dates, and sending notifications for holds and overdue items.
Preserve diagrams and example code from the original notes; the following design strictly uses the existing content and re-organizes it into the canonical OOD template.
Solution
1. Requirements Analysis
Functional Requirements:
- Search books by title, author, subject, or publication date.
- Add/remove/update books and book items (copies).
- Register and manage member accounts and librarian accounts.
- Check out, return, renew, and reserve book items.
- Enforce borrowing limits (e.g., max 5 books) and maximum lending period (e.g., 10 days).
- Calculate and collect fines for late returns.
- Send notifications when reserved books become available or when items are overdue.
Non-Functional Requirements:
- Consistency: Accurate tracking of book item state (available/reserved/loaned).
- Scalability: Efficient catalog search and support many concurrent members.
- Reliability: Ensure lending and reservation operations are durable and auditable.
- Extensibility: Support additional media types (ebooks, audiobooks), and integrate barcode scanners.
Constraints and assumptions:
- Each physical copy is modelled as a BookItem with a unique barcode.
- Reservations hold until the book is returned; reservation notifications are sent when a reserved copy becomes available.
- Business rules (e.g., max items and lending days) are configurable via constants.
2. Use Case Diagram
Actors: Librarian, Member, System
Top use cases: Add/Modify Book, Search Catalog, Register/Cancel Membership, Check-out Book, Reserve Book, Renew Book, Return Book
graph TD subgraph LibrarySystem UC1(Add/Remove/Edit Book) UC2(Search Catalog) UC3(Register/Cancel Membership) UC4(Check-out Book) UC5(Reserve Book) UC6(Renew Book) UC7(Return Book) end Librarian --> UC1 Member --> UC2 Member --> UC4 Member --> UC5 Member --> UC6 Member --> UC7 System --> UC5 System --> UC7
3. Class Diagram
Core classes and responsibilities (brief):
- Library: root entity that contains catalog and physical racks.
- Book: bibliographic metadata (ISBN, title, authors, format).
- BookItem: physical copy with barcode and status (available, reserved, loaned, lost).
- Account / Member / Librarian: user identities and operations they can perform.
- BookReservation: represents a reservation for a BookItem by a Member.
- BookLending: represents the checkout instance with due date.
- Fine: calculate and collect fines for overdue returns.
- Catalog / Search: indexing and search operations across collections.
- Notification: handles sending notifications (reserved available, overdue reminders).
classDiagram class Library { +String name +Address address } class Book { +String ISBN +String title +List<Author> authors +BookFormat format } class BookItem { +String barcode +BookStatus status +Date purchaseDate } class Account { +int id +AccountStatus status } class Member { +int memberId +Date dateOfMembership +int totalCheckedOut } class Librarian { } class BookReservation { +Date createdOn +ReservationStatus status } class BookLending { +Date borrowedOn +Date dueDate +Date returnedOn } class Fine { +collectFine(memberId, days) } class Catalog { +searchByTitle() +searchByAuthor() } class Notification { +sendNotification() } Account <|-- Member Account <|-- Librarian Book "1" -- "1..*" BookItem : copies Member "1" -- "0..*" BookReservation : reservations BookItem "1" -- "0..*" BookLending : lendings BookReservation "1" -- "1" BookItem : for BookLending "1" -- "1" BookItem : for
4. Activity Diagrams
Activity: Check-out a book
graph TD A[Member searches catalog] --> B[Select BookItem] B --> C{Is BookItem reference-only?} C -- Yes --> D[Reject checkout] C -- No --> E{Has member reached limit?} E -- Yes --> F[Reject checkout] E -- No --> G[Create BookLending, set due date] G --> H[Update BookItem status to LOANED] H --> I[Send checkout notification]
Activity: Return a book
graph TD R1[Member returns book] --> R2[Check for fines] R2 --> R3{Is overdue?} R3 -- Yes --> R4[Calculate & collect fine] R3 -- No --> R5[Update BookItem status to AVAILABLE] R4 --> R5 R5 --> R6[If reservations exist, notify next member]
5. High-Level Code Implementation
Below are skeletons (Python) that follow the original content and the Google style guidelines where practical. Java skeletons can be added on request.
from abc import ABC
from enum import Enum
from dataclasses import dataclass
from datetime import date, datetime
from typing import List, Optional
class BookFormat(Enum):
HARDCOVER = 1
PAPERBACK = 2
AUDIO_BOOK = 3
EBOOK = 4
class BookStatus(Enum):
AVAILABLE = 1
RESERVED = 2
LOANED = 3
LOST = 4
class ReservationStatus(Enum):
WAITING = 1
PENDING = 2
CANCELED = 3
NONE = 4
class AccountStatus(Enum):
ACTIVE = 1
CLOSED = 2
CANCELED = 3
BLACKLISTED = 4
@dataclass
class Address:
street: str
city: str
state: str
zip_code: str
country: str
class Account(ABC):
def __init__(self, id: int, password: str, person: object,
status: AccountStatus = AccountStatus.ACTIVE) -> None:
self._id = id
self._password = password
self._person = person
self._status = status
def reset_password(self) -> None:
pass
class Member(Account):
def __init__(self, id: int, password: str, person: object,
status: AccountStatus = AccountStatus.ACTIVE) -> None:
super().__init__(id, password, person, status)
self.date_of_membership: date = date.today()
self.total_books_checkedout: int = 0
def reserve_book_item(self, book_item: 'BookItem') -> None:
pass
def checkout_book_item(self, book_item: 'BookItem') -> bool:
# check limits and reservations
return True
class Book(ABC):
def __init__(self, ISBN: str, title: str, subject: str, publisher: str,
language: str, number_of_pages: int) -> None:
self._ISBN = ISBN
self._title = title
self._subject = subject
self._publisher = publisher
self._language = language
self._number_of_pages = number_of_pages
self._authors: List[str] = []
class BookItem(Book):
def __init__(self, barcode: str, is_reference_only: bool, borrowed: bool,
due_date: Optional[date], price: float, book_format: BookFormat,
status: BookStatus, date_of_purchase: date,
publication_date: date, placed_at: str) -> None:
super().__init__(ISBN="", title="", subject="", publisher="",
language="", number_of_pages=0)
self._barcode = barcode
self._is_reference_only = is_reference_only
self._borrowed = borrowed
self._due_date = due_date
self._price = price
self._format = book_format
self._status = status
self._date_of_purchase = date_of_purchase
self._publication_date = publication_date
self._placed_at = placed_at
def checkout(self, member_id: int) -> bool:
if self._is_reference_only:
return False
# delegate to BookLending
return True
class BookReservation:
def __init__(self, creation_date: datetime, status: ReservationStatus,
book_item_barcode: str, member_id: int) -> None:
self._creation_date = creation_date
self._status = status
self._book_item_barcode = book_item_barcode
self._member_id = member_id
def fetch_reservation_details(self, barcode: str) -> Optional['BookReservation']:
return None
class BookLending:
def __init__(self, creation_date: datetime, due_date: datetime,
book_item_barcode: str, member_id: int) -> None:
self._creation_date = creation_date
self._due_date = due_date
self._return_date: Optional[datetime] = None
self._book_item_barcode = book_item_barcode
self._member_id = member_id
@staticmethod
def lend_book(barcode: str, member_id: int) -> bool:
return True
class Fine:
@staticmethod
def collect_fine(member_id: int, days: int) -> None:
pass
class Catalog:
def __init__(self) -> None:
self._book_titles = {}
self._book_authors = {}
self._book_subjects = {}
self._book_publication_dates = {}
def search_by_title(self, query: str) -> List[Book]:
return self._book_titles.get(query, [])
def search_by_author(self, query: str) -> List[Book]:
return self._book_authors.get(query, [])
