Quantity = <number> Number .
Nonempty_Store_List = <it> Store [ <next> Nonempty_Store_List ] .
W : AA | EE .
ShoeOrder = <id> String <style> String <color> Ident <size> String <width> Width [ <stores> Store_List ] .
AA = extends W.
Store = <name> Ident <howManySuchShoes> Quantity .
Store_List = [ <first> Nonempty_Store_List ] .
Width = <w> W .
EE = extends W.