Design an object-oriented elevator control system for a building with multiple floors and multiple elevators. The system should support: - Hall requests from each floor, where a user can request to go up or down - Cabin requests from inside an elevator, where a user selects a destination floor - Tracking each elevator's current floor, direction, door state, and pending stops - Assigning hall requests to an appropriate elevator - Moving elevators efficiently while avoiding obviously poor scheduling decisions Focus on clean object-oriented design and the core scheduling logic. You do not need to model low-level motor hardware, networking, or a graphical UI. Discuss the main classes, responsibilities, state transitions, and how requests are processed. If useful, also describe a simple dispatch algorithm and how you would extend the design later.