A menu item will have only one complement. A menu item can be a complement to multiple menu items.
The issue I'm having here is with the compoiste key. A menu item is identified by Food outlet ID, Menu ID, Menu item name.
To associate a menu item with a complement, I think the following might suffice, but I not sure:
Food outlet ID(FK)
Menu ID (FK)
Menu item ID (FK)
Menu item complement ID (FK)
(each underlined attribute is a partial primary key).
The other issue here is, if the above is correct, the there is only one attribute in the difference between the complement entity and the menu item entity. Would it make sense and be correct in terms of normalization, if I were to place the complement attribute into the Menu item entity?