Security is a type of Department. Security is related to Homeland. 
Elevator is related to Passenger. Passenger is related to Car. Car is related to Motor. Motor is related to Auto. 
Department <--IsA-- Security <--RelatedTo--> Homeland 
Elevator <--RelatedTo--> Passenger <--RelatedTo--> Car <--RelatedTo--> Motor <--RelatedTo--> Auto 