EN
For a subset $E ⊆ ℝ^{d}$ and $x ∈ ℝ^{d}$, the local Hausdorff dimension function of E at x is defined by
$dim_{H,loc}(x,E) = lim_{r↘ 0} dim_{H}(E ∩ B(x,r))$
where $dim_{H}$ denotes the Hausdorff dimension. We give a complete characterization of the set of functions that are local Hausdorff dimension functions. In fact, we prove a significantly more general result, namely, we give a complete characterization of those functions that are local dimension functions of an arbitrary regular dimension index.