Abstract is a type of Concept. Concept is related to Danger. Danger is related to Difficulty. Wall is a type of Difficulty. 
Thanks is a type of Aid. Thanks is related to Manner. Manner is related to Gentle. 
Abstract --IsA--> Concept <--RelatedTo--> Danger <--RelatedTo--> Difficulty <--IsA-- Wall 
Aid <--IsA-- Thanks <--RelatedTo--> Manner <--RelatedTo--> Gentle 