Fellow is a different concept from Mate. Mate is a type of Animal. Animal is related to Blood. Blood is related to Inside. 
Job is related to Agent. Agent is related to Investigator. Investigator is a type of Expert. 
Fellow <--DistinctFrom--> Mate --IsA--> Animal <--RelatedTo--> Blood <--RelatedTo--> Inside 
Job <--RelatedTo--> Agent <--RelatedTo--> Investigator --IsA--> Expert 