There is no single, definitive preparation for pesto. It varies a bit from town to town in Liguria, just like a dialect. Even within a town there will be differences in how pesto is made. Every single pesto that you will ever taste is unique, because the ingredients used will differ as will the skill and preferences of the person making the sauce. Even if you were to give two cooks equal amounts of basil, olive oil, pine nuts, garlic, and cheese from the same sources, the results will not be the same because of the hand and eye of the person who makes the pesto.