Essential is related to Need. Need is related to Help. Mechanism can be used for Help. Control is a type of Mechanism. 
Script is a synonym of Hand. Hand is related to Elbow. Elbow is related to Bend. 
Essential <--RelatedTo--> Need <--RelatedTo--> Help <--UsedFor-- Mechanism <--IsA-- Control 
Script <--Synonym--> Hand <--RelatedTo--> Elbow <--RelatedTo--> Bend 