you are likely to find System in/at/on Place. Exhaust is a type of System. Exhaust is a type of Gas. Gas is related to Smell. 
Political is related to Minister. Minister is a type of Executive. Mayor is a type of Executive. 
Place <--AtLocation-- System <--IsA-- Exhaust --IsA--> Gas <--RelatedTo--> Smell 
Political <--RelatedTo--> Minister --IsA--> Executive <--IsA-- Mayor 