Quantum physics is an ab initio model because it starts from first principles. We try to solve the schrödinger equation by using physical constants only. Classical mechanics are based on Newton’s law of mechanics, also here it is based on first principles. I also think that classical electromagnetism is a ab initio model, which is based on Maxwell’s equations and Lorentz force law. However in semis/non classical electromagnetism there are also some semi-emperical laws, and these I think are not longer ab innate.