  We analyze the quantization of dynamical systems that do not involve any
background notion of space and time. We give a set of conditions for the
introduction of an intrinsic time in quantum mechanics. We show that these
conditions are a generalization of the usual procedure of deparametrization of
relational theories with hamiltonian constraint that allow to include systems
with an evolving Hilbert Space. We apply our quantization procedure to the
parametrized free particle and to some explicit examples of dynamical system
with an evolving Hilbert space. Finally, we conclude with some considerations
concerning the quantum gravity case.
