Comment by auggierose

There does not need to be a set of constraints for optimisation to be defined. You can talk about optimisation on an unconstrained domain, for example all of ℝ⨯ℝ. But there DOES need to be a measure function that measures what you are optimising for. The benefit of fraud would be one such function you could optimise for, and that seems to be what GP is after. The pure amount of fraud is a different one, which seems to be what you are interested in.