Given a quasi-concave-convex real-valued function f: X×Y --> R defined on the product of two convex sets we would like to know if inff_Y sup_X f = sup_X inff_Y f. We showed in another paper [A reconstruction of polytopes by convex pastings, to appear in Mathematika] that this question is very closely related to the following "reconstruction" problem: given a polytope (i.e. the convex hull of a finite set of points) X and a family F of subpolytopes of X, we would like to know if X is an element of F, knowing that any polytope which is obtained by cutting an element of F with a hyperplane or by pasting two elements of F along a common facet is also in F. Here, we consider a similar reconstruction problem for arbitrary convex sets.