Trail is related to Road. Road is related to Gate. Gate is related to Boundary. Edge is a type of Boundary. 
Investigate is a synonym of Examine. Examine is a synonym of Analyze. Diagnose is a type of Analyze. 
Trail <--RelatedTo--> Road <--RelatedTo--> Gate <--RelatedTo--> Boundary <--IsA-- Edge 
Investigate <--Synonym--> Examine <--Synonym--> Analyze <--IsA-- Diagnose 