A scan for models with realistic fermion mass patterns

Models are considered which have no small Yukawa couplings unrelated to symmetry. This situation is generic in higher dimensional unification where Yukawa couplings are predicted to have a strength similar to the gauge couplings. Generations have then to be differentiated by symmetry properties and the structure of fermion mass matrices is given in terms of quantum numbers alone. Possible symmetries leading to realistic mass matrices are scanned. (orig.)