HOPEX Information Architecture > Data Architecture > The data model > Normalization Rules > Second Normal Form
Second Normal Form
 
Rule: The value of an association attribute is set only when all the entities concerned are known.
If the car category is an attribute of the “Car Contract” association, this assumes that the car category may change from one contract to the next, which would not be very honest.
If the car category is to be independent of the contract, it must be an attribute of the “Car” entity.