The standard model Lagrangian is well known. But there are several ways to quantize a theory starting from the Lagrangian. In particular there are several ways to quantize gauge theories (e.g. canonical, Gupta-Bleuler, path integral, ...).
Which is the quantization scheme currently used in the standard model? Is it clear that this is the right way to quantize? What can be said about the commutation relations? And in which sense does gauge invariance hold?