+What are pegs? The term harks back to a 1986 paper by Fred Landman
+called `Pegs and Alecs'. Pegs are simply hooks for hanging properties
+on. Pegs are supposed to be as anonymous as possible. Think of
+hanging your coat on a physical peg: you don't care which peg it is,
+only that there are enough pegs for everyone's coat to hang from.
+Likewise, for the pegs of GSV, all that matters is that there are
+enough of them. (Incidentally, there is nothing in Gronendijk and
+Stokhof's original DPL paper that corresponds naturally to pegs; but
+in their Dynamic Montague Grammar paper, pegs serve a purpose similar
+to discourse referents there, though the connection is not simple.)
+
+Pegs can be highly useful for exploring puzzles of reference and
+coreference.
+
+ Standard assignment function System with Pegs (drefs)
+ ---------------------------- ------------------------
+ Variable Object Var Peg Object
+ --------- ------- --- --- ------
+ x --> a x --> 0 --> a
+ y -/ y -/
+ z --> b z --> 1 --> a
+
+A standard assignment function can map two different variables onto
+the same object. In the diagram, x and y are both mapped onto the
+object a. With discourse referents in view, we can have two different
+flavors of coreference. Just as with ordinary assignment functions,
+variables can be mapped onto pegs (discourse referents) that are in
+turn mapped onto the same object. In the diagram, x is mapped onto
+the peg 0, which in turn is mapped onto the object a, and z is mapped
+onto a discourse referent that is mapped onto a. On a deeper level,
+we can suppose that y is mapped onto the same discourse referent as
+x. With a system like this, we are free to reassign the discourse
+referent associated with z to a different object, in which case x and
+z will no longer refer to the same object. But there is no way to
+change the object associated with x without necessarily changing the
+object associated with y. They are coreferent in a deeper, less
+accidental sense.
+
+GSV could make use of this expressive power. But they don't. In
+fact, their system is careful designed to guarantee that every
+variable is assigned a discourse referent distinct from all previous
+discourse referents.
+
+The addition of pegs tracks an active discussion in the dynamic
+literature around the time of publication of the paper. Groenendijk
+and Stokhof (Two theories of dynamic semantics, 1989) noted that it
+was possible in DPL for information to be "lost".
+
+ 18. (∃x.P(x)) & (∃x.Q(x)) & R(x)
+
+If the two existentials happen to bind the same variable (here, "x"),
+then the second existential occludes the first. That is, at the point
+at which we evalute R(x), all of the assignment functions will be
+mapping the variable "x" to objects that have property Q. The
+information that there exist objects with property P has been lost.
+If you want your dynamic system to be eliminative---or in more general
+terms, if you want the amount of information embodied by an updated
+information state to be monotonically increasing---then this is a
+problem.
+
+A syntactic solution is to require that the variable bound
+by an existential to be chosen fresh.
+
+Vermeulen, Cees FM. "Merging without mystery or: Variables in dynamics
+semantics." Journal of Philosophical Logic 24.4 (1995): 405-450 offers
+a different approach, one based on *referent systems*. GSV's pegs are
+a referent system. In the pegs system, when (18) is processed, the
+information that there is an object that has property P is maintained
+in the information state. Curiously, however, there is still no way
+to refer to that object, at least, not with a variable, since there is
+no variable that is associated with the peg that points to the
+relevant object. So the information is present, but not accessible.
+
+That does not mean that there aren't other expression types that are
+able to latch onto peg. An intriguing suggestion based on an example
+in Vermeulen is that "former" might be able to provide access to a
+hidden peg:
+
+ 19. Someone entered. Someone spoke. The former was a woman.
+
+Presumably we want *the former* to be able to pick out the person who
+entered, whether or not the two existentials bind the same variable or
+not. If we allow "former" to latch onto the second most recently
+established peg, no matter whether there is a variable still pointing
+to that peg, the desired effect is achieved.
+
+But none of this is relevant for any of the explanations or analyses
+provide by the GSV fragment, and it is considerably simpler to see
+what their fragment is about if we leave referent systems out of it.