Definition 7.26.
A family \((X_i\to X)_i\) in \(C^{\ad}\) is a \(D\)-cover if it is a covering family for the canonical topology on \(C\) and satisfies universal \(!\)-descent: after every base change \(Y\to X\), the resulting family \((X_i\times_XY\to Y)_i\) satisfies descent for \(D^!\). The \(D\)-topology \(\tau_D\) is the topology whose covering families are the \(D\)-covers.