Vendor is related to Bar. Bar is related to Store. you are likely to find Stuff in/at/on Store. Stuff is related to Milk. 
Knife can be used for Butter. Knife is made of Steel. 
Vendor <--RelatedTo--> Bar <--RelatedTo--> Store <--AtLocation-- Stuff <--RelatedTo--> Milk 
Butter <--UsedFor-- Knife --MadeOf--> Steel 