Necessary statements and canonical forms

Consider the naming:

(Person which isOwnerOf Car) name CarOwner.

If we now look at the categories:

CarOwner.
CarOwner which hasAge old.

They will be the same. CarOwner already has the criterion hasAge old due to the necessary statement introduced earlier, so the system has reduced them to the same category.

Look at the criteria, the criterion hasAge old appears under conventional criteria because it is inherited from one of its ancestors in the subsumption hierarchy: Person which isOwnerOf RoadVehicle.

To summarise, a canonical form is a starting elementary category known as the base along with a collection of criteria in which all redundant information has been removed. If the GRAIL browser is invoked on a which expression, the compiler will reduce it to canonical form before opening the browser. The criteria are divided into three sections: the defining criteria; the necessary criteria which result from necessary statements about this specific category; and the inherited criteria which result from necessary statements, or definitions of categories, further up the hierarchy.