 Most proposals for dynamic versions of Montague grammar develop what are in fact higher order versions of dynamic predicate logic (DPL). This holds for Groenendijk and Stokhof 1990; Chierchia 1992, 1995; Muskens 1994, 1995, 1996; Eijck 1997; Eijck and Kamp 1997; Kohlhase et al. 1996; and Kuschert 2000. These systems all inherit a feature (or bug) from the DPL approach: they make re-assignment destructive. DRT does not suffer from this problem: the discourse representation construction algorithms of Kamp 1981 and Kamp and Reyle 1993 are stated in terms of functions with finite domains, and carefully talk about “taking a fresh discourse referent” to extend the domain of a verifying function, for each new noun phrase to be processed.