Guard is related to Agent. Agent is related to Spy. Spy is a synonym of Sight. 
Frown is a different concept from Smile. Smile is related to Face. Face is related to Entire. Entire is related to Story. 
Guard <--RelatedTo--> Agent <--RelatedTo--> Spy <--Synonym--> Sight 
Frown <--DistinctFrom--> Smile <--RelatedTo--> Face <--RelatedTo--> Entire <--RelatedTo--> Story 