  Measurements of the diffractive structure function, $F_2^D$, of the proton at
HERA are used to extract the partonic structure of the Pomeron. Regge
Factorization is tested and is found to describe well the existing data within
the selected kinematic range. The analysis is based on the next to leading
order QCD evolution equations. The results obtained from various data sets are
compared. An analysis of the uncertainties in determining the parton
distributions is provided. The probability of diffraction is calculated using
the obtained results.
