Storage is a type of Maintenance. Storage is related to Record. Record is related to Back. 
Sink is related to Drain. Drain is part of Toilet. Toilet is related to Waste. Exhaust is a type of Waste. 
Maintenance <--IsA-- Storage <--RelatedTo--> Record <--RelatedTo--> Back 
Sink <--RelatedTo--> Drain --PartOf--> Toilet <--RelatedTo--> Waste <--IsA-- Exhaust 