DP hypothesis of Abney (1987), the syntactic unit that had formerly been known as noun phrase should in fact be analyzed as a phrase headed by a determiner, hence the label DP. Quite independently of this syntactic development, Partee (1987) proposed a type shifting paradigm for the semantic analysis of nominals (now called DPs). In Partee's proposal DPs are ambiguous between a referential reading of type e, a predicative reading of type et and a quantificational reading of type (et)t. DP (...) meanings can flexibly move between their different readings due to covert application of semantic operators. The present paper proposes some strong relationships between these syntactic and semantic paradigms. It is argued that the structure of the DP affects its semantics in that the NP level within the DP is purely predicative and the DP level itself is purely quantificational. However, the intermediate D' level is flexible between the predicate/quantifier semantic categories, due to the covert application of semantic operators at this level. Partee's assumption, adopted from Discourse Representation Theory and more traditional approaches in philosophical logic, that some DPs need to have a (discourse) referential reading, is withdrawn. Instead of Partee's type shifting operators between the three semantic categories she assumes, two operators are used between predicates and quantifiers. The choice function operation of Reinhart (1997) and Winter (1997) is used as a general operator from predicates to quantifiers. The minimum operator of Winter (1996) is used as a general operator from quantifiers to predicates. These two operations, referred to as category shifting operators , account for most of the Partee data and substantially extend the theory of flexibility to treat some intricate phenomena in the domains of coordination, plurality and scope. (shrink)