2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/89602Axiomatic approach to measurement theory is developed. All the possible statistical properties of apparatuses measuring an observable with nondegenerate spectrum allowed in standard quantum mechanics are characterized.9 pages, LaTeX, invited talk at 5th Int'l Conf. on Quantum Communication, Measurement and Computing (Capri, Iatly, July 3--8, 2000)Quantum Physicstext