DESIGN LEVELS Conceptual Logical Physical What's actually in the game: players, matches, and items. No tables or types—just entities and the relationships between them. The same entities, but now in terms of the relational model: tables, keys, and relationships. A specific DBMS: data types, indexes, storage, and constraints. This is where PostgreSQL comes in. "The player has an inventory" inventory(player_id, item_id, quantity) quantity INTEGER CHECK (quantity > 0)