Factorization prescriptions and phenomenological applications of the parton model

We discuss the arbitrary conventions involved in formulating the QCD-aided parton model. The precise definition of constituent distribution and decay functions is seen to involve the choice of a factorization prescription. Just as in the case of a renormalization prescription, the choice of a factorization prescription can have phenomenological impact in that it can dramatically affect the size of higher-order corrections to calculations of physical observables. We present criteria based on next-to-leading order calculations for defining nonsinglet quark distributions. These can be seen to agree, in the appropriate limits, with speculations based on the resumming of certain ''large'' logarithmic corrections. We give a form of the Altarelli--Parisi equation suitable for directly calculating the evolution of a measurable structure function such as F2(x, Q2)