  QCD is the theory of strong interactions and non-perturbative methods have
been developed to address the confinement property of QCD. Many experimental
measurements probe the confining dynamics, and it is well-known that hard
scattering processes allow the extraction of non perturbative hadronic matrix
elements. To study exclusive hard processes, such as electromagnetic form
factors and reactions like gamma* N -> gamma N', gamma* N -> pi N', gamma*
gamma -> pi pi, antiproton proton ->gamma* pi in particular kinematics (named
as generalized Bjorken regime), one introduces specific non-perturbative
objects, namely generalized parton distributions (GPDs), distribution
amplitudes (DA) and transition distribution amplitudes (TDA), which are Fourier
transformed non-diagonal matrix elements of non-local operators on the
light-cone. We review here a selected sample of exclusive amplitudes in which
the quark and gluon content of hadrons is probed, and emphasize that much
remains to be done to successfully compute their non-perturbative parts. We
present some difficulties with respect to the application of the much
publicized AdS-QCD approach to the calculation of these partonic quantities.
