  High energy factorization predictions for F2^c are derived using BFKL
descriptions of the proton structure function F2 at HERA. The model parameters
are fixed by a fit of F2 at small x. Two different approaches of the non
perturbative proton input are shown to correspond to the factorization at the
gluon or quark level, respectively. The predictions for F2^c are in agreement
with the data within the present error bars. However, the photon wave-function
formulation (factorization at quark level) predicts significantly higher F2^c
than both gluon factorization and a next-leading order DGLAP model.
