It will be proposed that noun phrases contribute to the interpretation of sentences in two quite different ways: by introducing a logical subject of predication or by performing a (counting) operation on an independently defined predicate denotation. These will be called modes of operation. The denotational semantic properties of the noun phrase delimit, but do not fully determine, its available modes of operation. The distinction between the "subject of predication" mode and the "predicate operator" mode itself is likewise not purely denotational; rather, it corresponds to a difference in canonical verification procedures.
It will be proposed that Discourse Representation Theory (Kamp & Reyle 1993) may provide the representations in whose terms to define these procedures. Noun phrases that operate as subjects of predication are ones that introduce discourse referents, while predicate operators are beasts that behave as generalized quantifiers. These parallelisms suggest, in turn, that DRT need not be simply understood as a logic with a particular approach to variables, but may (should?) have a procedural flavor added to it.
On a more concrete note, the paper will propose to revise the standard DRT classification of noun phrases. It will be argued that a variety of distributive quantifiers that DRT associates duplex conditions with operate in the subject of predication mode and indeed exhibit diagnostics of introducing discourse referents (albeit somewhat different kinds than definites, etc.).