  We investigate the applicability of inhomogeneous absorber models in the
formation of AGN outflow absorption-troughs. The models we explore are limited
to monotonic gradients of absorbing column densities in front of a finite
emission source. Our main finding is that simple power-law and gaussian
distributions are hard pressed to fit the Mrk 279 high-quality UV outflow data.
An acceptable fit for the O VI troughs can only be obtained by assuming
unrealistic optical depth values (upward of 100). The strongest constraints
arise from the attempt to fit the Lyman series troughs. In this case it is
evident that even allowing for complete freedom of both the power-law exponent
and the optical depth as a function of velocity cannot yield an acceptable fit.
In contrast, partial covering models do yield good fits for the Lyman series
troughs. We conclude that monotonic inhomogeneous absorber models that do not
include a sharp edge in the optical depth distribution across the source are
not an adequate physical model to explain the trough formation mechanism for
the outflow observed in Mrk 279.
