 Transformations are modeled as functions acting on the entire space, meaning that every transformation must be applicable to every object.Lewin points out that this requirement significantly constrains the spaces and transformations that can be considered.For example, if the space S is the space of diatonic triads (represented by the Roman numerals I, ii, iii, IV, V, vi, and vii°), the "Dominant transformation" must be defined so as to apply to each of these triads.