diff --git a/networks.rkt b/networks.rkt
index 3008fc4..47e839a 100644
--- a/networks.rkt
+++ b/networks.rkt
@@ -1,7 +1,7 @@
 #lang racket
 
 (module typed typed/racket
-  (require "utils.rkt" "functions.rkt"
+  (require "utils.rkt" "functions.rkt" "dynamics.rkt"
            typed/graph racket/random)
 
   (module+ test
@@ -33,7 +33,7 @@
    build-interaction-graph/form build-signed-interaction-graph
    build-signed-interaction-graph/form
 
-   Modality Mode
+   Modality Mode dynamics%
    )
 
   (define-type (State a) (VariableMapping a))
@@ -512,6 +512,41 @@
 
   (define-type Modality (Listof Variable))
   (define-type Mode (Listof Modality))
+
+  (define dynamics%
+    ;; TODO: Fix the parameter of State when Typed Racket supports
+    ;; passing type parameters to the parent.
+    (class (inst dds% (State Any) Modality)
+      #:forall (a)
+      (super-new)
+
+      (init-field [network : (Network a) network]
+                  [mode : Mode mode])
+
+      (: step/annotated (-> (State a) (Listof (Pairof Modality (State a)))))
+      (define/override (step/annotated s)
+        (for/list ([m mode])
+          (cons m (update network s m))))))
+
+  (module+ test
+    (test-case "dynamics%"
+      (define n1 : (Network Boolean)
+        (forms->boolean-network (hash 'x '(not y)
+                                      'y 'x
+                                      'z '(and y z))))
+      (define syn : Mode '((x y z)))
+      (define asyn : Mode '((x) (y) (z)))
+      (define dyn-syn (new (inst dynamics% Boolean) [network n1] [mode syn]))
+      (define dyn-asyn (new (inst dynamics% Boolean) [network n1] [mode asyn]))
+
+      (define s1 (hash 'x #f 'y #f 'z #f))
+      (check-equal? (send dyn-syn step/annotated s1)
+                    '(((x y z) . #hash((x . #t) (y . #f) (z . #f)))))
+      (check-equal? (send dyn-asyn step/annotated s1)
+                    '(((x) . #hash((x . #t) (y . #f) (z . #f)))
+                      ((y) . #hash((x . #f) (y . #f) (z . #f)))
+                      ((z) . #hash((x . #f) (y . #f) (z . #f)))))
+      ))
   )
 
 (require 'typed)
diff --git a/scribblings/networks.scrbl b/scribblings/networks.scrbl
index d5d216c..623c993 100644
--- a/scribblings/networks.scrbl
+++ b/scribblings/networks.scrbl
@@ -3,9 +3,11 @@
 	  (for-label typed/racket/base
 	  	     graph
 		     (only-in typed/graph Graph)
+		     (only-in racket/class send)
 		     (submod "../networks.rkt" typed)
 		     "../utils.rkt"
-		     "../functions.rkt"))
+		     "../functions.rkt"
+		     "../dynamics.rkt"))
 
 @(define networks-evaluator
   (parameterize ([sandbox-output 'string]
@@ -376,6 +378,38 @@ A mode is a list of modalities.  This is a synonym of @racket[(Listof Modality)]
 
 }
 
+@defclass[dynamics% dds% ()]{
+
+A model of dynamics of a network is a @racket[Network] with a @racket[Mode].
+
+@defconstructor[([network (Network a)] [mode Mode])]{
+
+Creates a new instance of @racket[dynamics%] from a @racket[network] and
+a @racket[mode].  Both are available as public fields of the class.
+
+}
+
+@defmethod[(step/annotated [st (State a)]) (Listof (Pairof Modality (State a)))]{
+
+Apply the network stored in this class to the state @racket[st] with all
+modalities of the mode stored in this class.
+
+This is the only method of @racket[dds%] overridden in this class.
+
+@ex[
+(let* ([n (forms->boolean-network (hash 'a '(and a b)
+                                        'b '(not b)))]
+       [syn '((a) (b))]
+       [syn-dynamics (new (inst dynamics% Boolean) [network n] [mode syn])]
+       [st (hash 'a #f 'b #f)])
+  (send syn-dynamics step/annotated st))
+]
+
+}
+
+}
+
+
 @section{Inferring interaction graphs}
 
 This section provides inference of both unsigned and signed interaction graphs.