following description, showing the actors, use cases and the relationships between them. A campus housing system is a system used by universities to allow students to book apartments, especially students who don't live in the city of the university. Some people in the city add their available apartments to the campus housing to benefit from student rental as additional income. The system has the following functionality: - Allow the apartment owner to add his/her apartment to the campus housing, involving checking the identity of the owner. - Allow the apartment owner to delete his/her apartment from the campus housing, involving checking the identity of the owner. - Allow the student to search for an available apartment, where the user can search by location or by price. However, the system rarely failed to find an available apartment. - In a hospital, there are different clinics. - The hospital contains many doctors. - A doctor can be a consultant or a specialist doctor. - A doctor can work exactly in one clinic. - The hospital is visited by many patients. - Every doctor treats many patients, and a patient can be treated by one or more doctors