Principles for Relations

x has only y of a more general z

Sometimes it is necessary to express something like: A gasoline vehicle is a vehicle that has only a gasoline engine but no other motor. This can be expressed as an axiom with two parts (with gasoline engine being a subclass of motor:

(1) 'gasoline vehicle' 'has part' some 'gasoline engine' and

(2) 'gasoline vehicle' 'has part' only ( 'gasoline engine' or not motor )

As a vehicle has also other parts like e.g. four wheels and a driver's seat, the axiom gasoline vehicle has part only gasoline engine would not be sufficient. This would mean that the vehicle does any other parts.