“…The separation between the two suitable subsets is proved by showing that they lie in two disjoint level sets of a separating functional. Since then, ISA is extensively applied to establish separation theorems and theorems of alternative of constrained extremum problems by various kinds of separation functions such as linear and nonlinear cases, and then, Kuhn-Tucker type, Fritz-John type and Lagrangian-type optimality conditions of the constrained extremum problems are established by the corresponding theorems of separation and theorems of alternative; see [6,28,33,11,12,13,14,15,20,21,29,16,30]. Compared with the existing other approaches, a prominent advantage of ISA is that it can be applied to deal with nonconvex, nonsmooth and even discontinuous constrained optimization problems from the perspective of geometry.…”