  The holographic principle and the thermodynamics of de Sitter space suggest
that the total number of fundamental degrees of freedom associated with any
finite-volume region of space may be finite. The naive picture of a short
distance cut-off, however, is hardly compatible with the dynamical properties
of spacetime, let alone with Lorentz invariance. Considering the regions of
space just as general ``subsystems'' may help clarifying this problem. In usual
QFT the regions of space are, in fact, associated with a tensor product
decomposition of the total Hilbert space into ``subsystems'', but such a
decomposition is given a priori and the fundamental degrees of freedom are
labelled, already from the beginning, by the spacetime points. We suggest a new
strategy to identify ``localized regions'' as ``subsystems'' in a way which is
intrinsic to the total Hilbert-space dynamics of the quantum state of the
fields.
