diff --git a/dynamics.rkt b/dynamics.rkt
index d61780d..34f3a8d 100644
--- a/dynamics.rkt
+++ b/dynamics.rkt
@@ -1,2 +1,32 @@
 #lang typed/racket
 
+(require "utils.rkt" typed/graph)
+
+(provide dds%)
+
+(define dds%
+  (class object%
+    #:forall (State Modality)
+    (super-new)
+
+    (: step (-> State (Listof State)))
+    (define/abstract/error (step st))
+
+    (: step/annotated (-> State (Listof (Pairof Modality State))))
+    (define/abstract/error (step/annotated st))
+
+    (: step* (-> (Listof State) (Listof State)))
+    (define/abstract/error (step* sts))
+
+    (: build-state-graph (-> (Listof State) Graph))
+    (define/abstract/error (build-state-graph sts))
+
+    (: build-state-graph/annotated (-> (Listof State) Graph))
+    (define/abstract/error (build-state-graph/annotated sts))
+
+    (: build-state-graph* (-> (Listof State) Integer Graph))
+    (define/abstract/error (build-state-graph* sts nsteps))
+
+    (: build-state-graph*/annotated (-> (Listof State) Integer Graph))
+    (define/abstract/error (build-state-graph*/annotated nsteps sts))
+    ))
diff --git a/scribblings/dynamics.scrbl b/scribblings/dynamics.scrbl
index 554f27e..15f9030 100644
--- a/scribblings/dynamics.scrbl
+++ b/scribblings/dynamics.scrbl
@@ -1,7 +1,8 @@
 #lang scribble/manual
 
 @(require scribble/example racket/sandbox
-	  (for-label typed/racket/base))
+	  (for-label "../dynamics.rkt" typed/racket/base
+	  	     (only-in racket/class object%)))
 
 @(define-syntax-rule (deftypeform . args)
   (defform #:kind "type" . args))
@@ -16,3 +17,95 @@
 This module provides a number of general definitions for building and analyzing
 the dynamics of discrete dynamical systems.
 
+@defclass[dds% object% ()]{
+
+The abstract base class for discrete dynamical systems.
+
+This class has two type parameters:
+
+@itemize[
+
+@item{@racket[State] --- a state of the discrete dynamical system,}
+
+@item{@racket[Modality] --- a description of the way in which the discrete
+dynamical system transitions from a given state @italic{s} to another state
+@italic{s}.  For systems whose states are described by a set of variables,
+a @racket[Modality] is typically a list of variables updated during the
+state transition.}
+
+]
+
+@defmethod[(step [st State]) (Listof State)]{
+
+Given a state @racket[st], produces the next states of the state.
+
+This method falls back to calling @method[dds% step/annotated], and then
+discarding the annotations.
+
+}
+
+@defmethod[(step/annotated [st State]) (Listof (Pairof Modality State))]{
+
+Given a state, produces the next states paired with the corresponding
+modalities. Typical usage would include giving the information about the
+update mode.
+
+This method has no fallback and must be overridden.
+
+}
+
+@defmethod[(step* [sts (Listof State)]) (Listof State)]{
+
+Given a set of starting states, produce the set of states reachable in
+one step.
+
+This method falls back to running @method[dds% step] for all states.
+
+Note that @method[dds% step*] has no direct @tt{/annotated} counterpart.
+This is because producing a list of @racket[(Pairof Modality State)] would not
+give enough information to identify to which particular transition the modality
+corresponds to.
+
+}
+
+@defmethod[(build-state-graph [sts (Listof State)]) Graph]{
+
+Given a set of starting states, produces the state graph reachable from the
+starting states.
+
+This method falls back to exploring the state graph with @method[dds% step].
+
+}
+
+@defmethod[(build-state-graph/annotated [sts (Listof State)]) Graph]{
+
+Given a set of starting states, produces the labelled state graph reachable
+from the starting states.
+
+This method falls back to exploring the state graph with @method[dds%
+step/annotated].
+
+}
+
+@defmethod[(build-state-graph* [sts (Listof State)] [nsteps Integer]) Graph]{
+
+Given a set of starting states and a number @racket[nsteps] of steps to run,
+produces the state graph reachable from the starting states @racket[nsteps] steps.
+
+This method falls back to exploring the state graph with @method[dds% step].
+
+}
+
+@defmethod[(build-state-graph*/annotated [sts (Listof State)] [nsteps Integer])
+					 Graph]{
+
+Given a set of starting states and a number @racket[nsteps] of steps to run,
+produces the labelled state graph reachable from the starting states
+@racket[nsteps] steps.
+
+This method falls back to exploring the state graph with @method[dds%
+step/annotated].
+
+}
+
+}