We formulate necessary and sufficient conditions for a symplectic tomogram of
a quantum state to determine the density state. We establish a connection
between the (re)construction by means of symplectic tomograms with the
construction by means of Naimark positive-definite functions on the
Weyl-Heisenberg group. This connection is used to formulate properties which
guarantee that tomographic probabilities describe quantum states in the
probability representation of quantum mechanics.Comment: 10 pages,latex,submitted to Physics Letters