SAP Message 1W040 - Key definition of &1 is incompatible with supertype &2

Diagnosis
The key definition of the given object is not correct for thesupertype.

System Response
The object is not assigned to the supertype.

Procedure
You can only assign objects to supertypes that have the same keydefinitions for the primary key, that is the same DDIC references forthe fields of the primary key.