In this paper I confirm the hypothesis that NPs are dominated by a fun
ctional projection, the determiner phrase: I argue that the DP-hypothe
sis is crucial for the full unification of clauses and nominals not on
ly with respect to basic and derived positions of maximal projections,
but also with respect to both barrierhood and relativized minimality.
The former extractability hierarchy as well as the former specificity
condition are shown to be a function of a theory splitting lexical an
d functional information in combination with a theory that makes use o
f barrierhood and relativized minimality. The proposed account does no
t claim that the functional head D imposes exactly the same range of c
onditions as the functional heads INFL and/or COMP; I show in particul
ar that there is no extended projection principle inside DP and that D
restricts the maximal projections and traces occurring in its specifi
er to XPs compatible with genitive case. Eventually, the differences b
etween extractions out of clauses and extractions out of nominals foll
ow from differences between D and I and/or C with respect to the allow
ed content of their specifier.