  We present a method which allows to extract theoretical informations out of a
limited set of experimental data and observables, forming up in general an
under- constrained system. It has been applied to the field of nucleon
structure, in the domain of Generalized Parton Distributions (GPDs). We take
advantage of this review to remove a couple of approximations that we used in
our previous works and update our results using the latest data published.
