Chat messaging system UML class diagram modeling users, roles, permissions, messages, notifications, and group chats with junction tables for many-to-many relationships. User entities connect to Role and Permission through UserRole and RolePermission junction tables, establishing a role-based access control (RBAC) foundation. Messages flow from Users to Chats and trigger Notifications, while ChatParticipant junctions manage group membership and participant roles. Fork this diagram to customize entity relationships, add message encryption fields, or extend with read receipts and typing indicators for your messaging platform.