Can functional dependencies be "inversed"

Question

Say I have a situation where a person who is uniquely defined by their firstName and lastName can rent a car uniquely defined by its licensePlateNumber and dayOfRental.

Can I say both of these statements capture the domain requirement?

firstName, lastName -> licensePlateNumber, dayOfRental 
licensePlateNumber, dayOfRental -> firstName, lastName

Is there a difference between the two?

Answer 1

First, there's clearly a difference between {firstName, lastName}->{licensePlateNumber, type} and {licensePlateNumber, type}->{firstName, lastName}. In symbolic notation, you'd have A->B and B->A. Those two are clearly different.

Second, both those together do seem to capture the requirement you're interested in.

Third, I'd expect license plate number alone to uniquely identify a car. But that doesn't change the substance of your question or of my answer.