Standard key structs are generated for entity classes and contain those attributes in the class whose stereotype is key. If no such attributes exist in the class then a standard key struct is not generated.
This struct will be used as a parameter for operations requiring a primary key. For example, reads and deletes.
Though standard key structs do not appear in the input meta-model they can be used as arguments to operations in the input meta-model. The name given to standard key structs is the name of the corresponding entity with the word Key appended. For example, the standard key struct for the class Employer would be called EmployerKey.