Physics in (canonical) quantum gravity needs to be manifestly
diffeomorphism-invariant. Consequently, physical observables need to be
formulated in terms of manifestly diffeomorphism-invariant operators, which are
necessarily composite. This makes an evaluation in general involved, even if
the concrete implementation of quantum gravity should be treatable
(semi-)perturbatively in general. A mechanism developed by Fr\”ohlich, Morchio
and Strocchi for flat-space-time quantum field theory may also be applicable in
this case. It may be possible to test this mechanism with methods like
dynamical triangulation.
