Library website UML class diagram modeling a three-tier user hierarchy with Student and Librarian inheriting from a base User class, each with distinct responsibilities and methods. Student entities initiate Transactions to reference Books, while Librarians manage Book inventory through update operations; the User base class provides shared authentication and profile attributes. This inheritance-based design demonstrates proper abstraction and separation of concerns, reducing code duplication and enforcing consistent user identity management across the system. Fork this diagram on Diagrams.so to customize entity relationships, add additional user roles, or extend the Transaction model with fine-grained borrowing rules. Consider adding a Reservation class to handle waitlisted books or a Fine entity to model overdue penalties.