Salt is related to Food. Butter is a type of Food. Butter is related to Smooth. Smooth is related to Texture. 
Sentence entails/necessarily involves Convict. Convict is a synonym of Inmate. Inmate is the opposite of Guard. 
Salt <--RelatedTo--> Food <--IsA-- Butter <--RelatedTo--> Smooth <--RelatedTo--> Texture 
Sentence --Entails--> Convict <--Synonym--> Inmate <--Antonym--> Guard 