  We discuss techniques and results for the extraction of the nucleon's
spin-dependent parton distributions and their uncertainties from data for
polarized deep-inelastic lepton-nucleon and proton-proton scattering by means
of a global QCD analysis. Computational methods are described that
significantly increase the speed of the required calculations to a level that
allows to perform the full analysis consistently at next-to-leading order
accuracy. We examine how the various data sets help to constrain different
aspects of the quark, anti-quark, and gluon helicity distributions. Uncertainty
estimates are performed using both the Lagrange multiplier and the Hessian
approaches. We use the extracted parton distribution functions and their
estimated uncertainties to predict spin asymmetries for high-transverse
momentum pion and jet production in polarized proton-proton collisions at 500
GeV center-of-mass system energy at BNL-RHIC, as well as for W boson
production.
