  It is argued that substantial portions of both Newtonian particle mechanics
and general relativity can be viewed as relational (rather than absolute)
theories. I furthermore use the relational particle models as toy models to
investigate the problem of time in closed-universe canonical quantum general
relativity. I consider thus in particular the internal time, semiclassical and
records tentative resolutions of the problem of time.

General Relativity and Quantum Cosmology