Economist is a type of Person. Person is related to Singer. Singer is related to Occupation. 
Use is related to Soap. Soap is related to Fat. Fat is similar to Protein. Protein is related to Fish. 
Economist --IsA--> Person <--RelatedTo--> Singer <--RelatedTo--> Occupation 
Use <--RelatedTo--> Soap <--RelatedTo--> Fat <--SimilarTo--> Protein <--RelatedTo--> Fish 