  Vignale and Kohn have recently formulated a local density approximation to
the time-dependent linear response of an inhomogeneous electron system in terms
of a vector potential for exchange and correlation. The vector potential
depends on the induced current density through spectral kernels to be evaluated
on the homogeneous electron-gas. After a brief review of their theory, the case
of inhomogeneous Bose superfluids is considered, with main focus on dynamic
Kohn-Sham equations for the condensate in the linear response regime and on
quantal generalized hydrodynamic equations in the weak inhomogeneity limit. We
also present the results of calculations of the exchange-correlation spectra in
both electron and superfluid boson systems.
