All, except the empty set case. Eventually you might need to investigate further to see if one such set was consistant with other information--order and delivery notes etc.--but initially, just whether any such (non-empty) set existed might be a useful boolean. But it would be rendered meaningless if the empty set is considered a match.

In truth, it was just the first example I thought of that supported my argument. However, hard as I might try, I cannot think of a counter example. Not one.