  The flavor-dependent valence, sea quark and antiquark spin distributions can
be determined separately from theoretical assumptions and experimental data. We
have determined the valence distributions using the Bjorken sum rule and have
extracted polarized sea distributions, assuming that the quarks and anti-quarks
for each flavor are symmetric. Other experiments have been proposed which will
allow us to completely break the SU(3) symmetry of the sea flavors. To create a
physical model for the polarized gluons, we investigate the gluon spin
asymmetry in a proton, $A_G(x,Q^2)={{\Delta G(x,Q^2)}\over {G(x,Q^2)}}$. By
assuming that htis is is approximately $Q^2$ invariant, we can completely
determine the $x$-dependence of this asymmetry, which satisfies constituent
counting rules and reproduces the basic results of the Bremsstrahlung model
originated by Close and Sivers. This asymmetry can be combined with the
measured unpolarized gluon density, $G(x,Q^2)$ to provide a prediction for
$\Delta G(x,Q^2)$. Existing and proposed experiments can test both the
prediction of scale-invariance for $A_G(x,Q^2)$ and the nature of $\Delta G$
itself. These models will be discussed along with suggestions for specific
experiments which can be performed at energies typical of HERA, RHIC and LHC to
determine these polarized distributions.
