  Using two alternative [O/H]-[Fe/H] dependences, the empirical oxygen
abundance distribution (EGD) is deduced from two different samples of old
objects, available in the literature. Under the assumption that each
distribution (with the addition of a third one previously known) is typical for
the corresponding subsystem, the EGD of the Galactic spheroid is determined
weighting by mass. A fit to the data is provided by simple models of chemical
evolution implying both homogeneous and inhomogeneous mixing, where star
formation is inhibited during halo formation and enhanced during bulge
formation, with respect to the disk. The theoretical oxygen abundance
distribution (TGD) is first determined for the halo and the bulge separately,
and then for the Galactic spheroid weighting by mass. Simple models implying
inhomogeneous mixing are able to fit an empirical age-metallicity relation
(EAMR) recently determined from a homogeneous sample of globular clusters,
which shows a non monotonic trend characterized by large dispersion. Some
possible implications related to the formation of Galactic spheroid and disk
are also discussed.
