  The minimal standardizer of a curve system on a punctured disk is the minimal
braid that transforms it into a system formed only by round curves. We give an
algorithm to compute it in a geometrical way. Then, we generalize this problem
algebraically to parabolic subgroups of Artin-Tits groups of spherical type and
we show that, to compute the minimal standardizer of a parabolic subgroup, it
suffices to compute the $pn$-normal form of a particular central element.
