This section takes the example in One definition keyed by another further. Each “Car Model” has a version: for example, you can buy a Mustang Coupe, a Convertible, a GT Coupe, a GT Convertible, a Mach 1, or SVT Cobra.
This could be an ever changing list, so it is a definition type (instead a static LIST). Call the definition type “Car Version”. When a user creates a “Car Version”, they also have to specify its “Car Brand” and “Car Model” (because there might be many “Car Models with a GT).
