Sidewalk can be Smooth. Float is a type of Smooth. 
Spill is related to Drop. Drop is related to Part. Part is related to Shoulder. Shoulder is a type of Raise. 
Sidewalk --HasProperty--> Smooth <--IsA-- Float 
Spill <--RelatedTo--> Drop <--RelatedTo--> Part <--RelatedTo--> Shoulder --IsA--> Raise 