  We address the problem of information completeness of quantum measuremets in
connection to quantum state tomography and with particular concern to quantum
symplectic tomography. We put forward some non-trivial situations where
informationally incomplete set of tomograms allows as well the state
reconstruction provided to have some a priori information on the state or its
dynamics. We then introduce a measure of information completeness and apply it
to symplectic quantum tomograms.
