  We analyse local models at the point of E_8 in F-theory GUTs and identify
exactly two models with potentially realistic properties concerning proton
stability and a suitable pattern of quark and lepton masses. To this end we
identify a matter parity at the local point. A globally consistent ultraviolet
completion turns out to be problematic for both models. It is impossible to
embed the models in a semilocal scheme via the spectral cover approach. This
seems to severely limit the predictive power of local model building and to
indicate that the full string theory might give us valuable hints for particle
physics model building.
