Soil is etymologically related to Sole. Clay is a type of Soil. Clay is a type of Ground. Ground is related to Surface. 
Welfare is related to System. you are likely to find System in/at/on Shop. you are likely to find Worker in/at/on Shop. Senator is a type of Worker. 
Sole <--EtymologicallyRelatedTo-- Soil <--IsA-- Clay --IsA--> Ground <--RelatedTo--> Surface 
Welfare <--RelatedTo--> System --AtLocation--> Shop <--AtLocation-- Worker <--IsA-- Senator 