“…By the time and demand of use and applications, variants of this property have emerged suitable to practical problems. Weaker/stronger versions: calmness, (strong) (Hölder) metric sub/regularity, semiregularity or equivalent versions: pseudo Lipschitz, linear openness were studied and have proved to have an important role in various applications in Mathematics, especially in Variational Analysis and Optimization [5,12,13,[15][16][17]26], ... Another direction in this line is to build directional models for these objects as recently proposed by Arutyunov-Avakov-Izmailov [1], Gfrerer [8], Ngai-Théra [20], Ngai-Tron-Théra [22], Ngai-Tron-Tinh [23]. Characterizations of these concepts have been established and successfully applied to study optimality conditions for mathematical programs, for calculating tangent cones,...This notion of directional regularity is an extension of an earlier notion used by Bonnans and Shapiro [3] to study sensitivity analysis.…”