  We deal with aspects of the direct and inverse problems in parameterized
Picard-Vessiot (PPV) theory. It is known that, for certain fields, a linear
differential algebraic group (LDAG) G is a PPV Galois group over these fields
if and only if G contains a Kolchin-dense finitely generated group. We show
that, for a class of LDAGs G, including unipotent groups, G is such a group if
and only if it has differential type 0. We give a procedure to determine if a
parameterized linear differential equation has a PPV Galois group in this class
and show how one can calculate the PPV Galois group of a parameterized linear
differential equation if its Galois group has differential type 0.
