Formal Subsumption

We've already met asserted subsumption, which is where the subsumption is asserted using newSub. For instance, a Car is a kind of RoadVehicle. The other type of subsumption is what is known as formal subsumption. This is where the relationship arises due to the structure of categories and is derived by the internal semantics of GRAIL.

In the earlier example, the category (Person which isDriverOf Car) is formally subsumed by (remember the direction!) Person.

One rule about formal subsumptions is that: any category X always subsumes any category of the form X which hasSomeAttribute Y.

There are other rules which define formal subsumption. We'll not go into detail here, but will return to this topic once we have introduced a few more attributes.