Let B-n denote the unit ball of C-n, n >= 1, and let D denote a finite product of B-nj, j >= 1. Given a non-constant holomorphic function b: D -> B-1, we study the corresponding family sigma(alpha) [6], alpha is an element of partial derivative B-1, of Clark measures on the distinguished boundary partial derivative D. We construct a natural unitary operator from the de Branges-Rovnyak space H(b) onto the Hardy space H-2 (sigma(alpha)). As an application, for D = B-n and an inner function I: B-n -> B-1, we show that the property sigma(1)[f] << sigma(1)[b] is directly related to the membership of an appropriate explicit function in H(b).