The Milky Way's Stellar Disk
  A suite of vast stellar surveys mapping the Milky Way, culminating in the
Gaia mission, is revolutionizing the empirical information about the
distribution and properties of stars in the Galactic stellar disk. We review
and lay out what analysis and modeling machinery needs to be in place to test
mechanisms of disk galaxy evolution and to stringently constrain the Galactic
gravitational potential, using such Galactic star-by-star measurements. We
stress the crucial role of stellar survey selection functions in any such
modeling; and we advocate the utility of viewing the Galactic stellar disk as
made up from `mono-abundance populations' (MAPs), both for dynamical modeling
and for constraining the Milky Way's evolutionary processes. We review recent
work on the spatial and kinematical distribution of MAPs, and lay out how
further study of MAPs in the Gaia era should lead to a decisively clearer
picture of the Milky Way's dark matter distribution and formation history.
