The first semantic objects that you define are the entities for the application. An entity is a real-world object, referred to by a noun (person, place, thing, or idea), for example, people, cities, products, shipments, and so forth. In databases, major entities are most often represented by tables and sometimes by fields. Minor entities are represented by fields. (You can also define domain commands, which aren’t related to a database, but perhaps to a piece of hardware such as a compact disk player. Domain commands allow requests such as “Play the album with song XXX on it.”)
