BookCycle Tunisia ER diagram models a peer-to-peer book exchange platform with users, books, requests, and exchanges as core entities. Users own books and initiate requests or exchanges; school_classes and subjects provide taxonomy for book categorization and discovery. The schema captures book condition, pricing, exchange status, and notifications to track user interactions end-to-end. Fork this diagram to customize for your own community book-sharing application or adapt the user-book-request-exchange pattern for rental or lending platforms. The design supports role-based access control and activity tracking via is_active flags and timestamp fields.