I was discussing the deconstruction of pizza the other day, to me convention is a bit of bread and cheese, dipped in a bit of leftover pasta sauce. We can go farther back if we want to but pizza was most definitely created by a restaurant worker after a busy dinner service. Or perhaps during
We might call pizza without cheese unconventional, but others might simply call it the marinara.
In short, pizza defies convention because it is new every time.