Results are established concerning the non-local solubility and well posedn
ess in various function spaces of the mixed problem for the Korteweg-de Vri
es equation
u(t) + u(xxx) + au(x) + uu(x) = f(t, x)
in the half-strip (0,T) x (-infinity,0). Some a priori estimates of the sol
utions are obtained using a special solution J(t, x) of the linearized Kdv
equation of boundary potential type. Properties of J are studied which diff
er essentially as x --> +infinity or x --> -infinity. Application of this b
oundary potential enables us in particular to prove the existence of genera
lized solutions with non-regular boundary values.