The plant produces a number of car makes, and each make is identified by a make name (e.g. Escort) and its year. In addition, a make has a chassis type (Sedan, Wagon, etc.). New make design is not done at the plant. When the Ford company approves a new design for production, a plant official must enter the information about the new make.
The manufacturing manager tracks the number of vehicles produced of each make. She is responsible for assigning each new vehicle a unique vehicle identifier. To ensure uniqueness, a list of all existing vehicle identifiers is maintained.
Consider the following ER diagram that has been proposed as a design for this information. What's wrong in the diagram?