: Represented as rectangles, these are the "nouns" of the system, such as Customer , Order , or Product .
: Analysts use them to identify logic errors in existing database structures. AZ erdЕ‘rЕ‘l
: They serve as high-level documentation of a system’s information architecture. Levels of Abstraction : Represented as rectangles, these are the "nouns"
: Adds more detail, defining attributes and keys but remaining independent of a specific database technology. : Represented as rectangles