  A definition of qualitative robustness for point estimators in general
statistical models is proposed. Some criteria for robustness are established
and applied to estimators in parametric, semiparametric, and nonparametric
models. In specific nonparametric models, the proposed definition boils down to
Hampel robustness. It is also explained how plug-in estimators in certain
nonparametric models can be reasonably classified w.r.t. their degrees of
robustness.
