  We present a model of generalised parton distributions based on a forward
ansatz in the DGLAP region. We discuss some aspects of the parametrisations, as
the dependence in t, with factorised and non-factorised approaches, where t is
the square of the four-momentum exchanged at the hadron vertex. The predictions
of this model are then compared with DVCS cross sections from H1 and ZEUS, and
a related observable, the skewing factor, defined as the following ratio
imaginary amplitudes : $R \equiv {Im {\cal A} (\gamma^*+p \to \gamma
+p)\lfrestriction{t=0}} / {Im {\cal A} (\gamma^*+p \to \gamma^*
+p)\lfrestriction{t=0}}$. It is an interesting quantity including both the
non-forward kinematics and the non-diagonal effects. Finally, we discuss the
beam charge asymmetry, which is certainly the most sensitive observable to the
different hypothesis needed in the GPDs parametrisations. We show that the
approximations done for the t dependence lead to significant differences for
the predictions in the HERMES kinematic domain and prospects are given for
COMPASS.
