Professional is related to Nurse. you are likely to find Nurse in/at/on Hospital. you are likely to find Hospital in/at/on City. 
Agent is a type of Substance. Ambassador is etymologically related to Agent. Ambassador is related to Diplomatic. Diplomatic is related to Ally. 
Professional <--RelatedTo--> Nurse --AtLocation--> Hospital --AtLocation--> City 
Substance <--IsA-- Agent <--EtymologicallyRelatedTo-- Ambassador <--RelatedTo--> Diplomatic <--RelatedTo--> Ally 