Quantum Physics seems to me an ab-initio model, as it is based on basic assumption which can not reduced further with the language to describe things as mathematics.
Classical Physics on the same way is ab-inito science with the limitation of applicability only on scales of low velocities etc.
Classical electromagnetism, not as a whole is ab-initio model, as its laws are also based on forces and acceleration of charges, Lorentz force etc…