diff --git a/networks.rkt b/networks.rkt
index be033e1..697b34c 100644
--- a/networks.rkt
+++ b/networks.rkt
@@ -102,7 +102,8 @@
                [tbf/state-tabulate (->* (tbf/state?) (#:headers boolean?)
                                         (listof (listof (or/c symbol? number?))))]
                [make-tbn (-> (listof (cons/c variable? tbf/state?)) tbn?)]
-               [tbn->network (-> tbn? network?)])
+               [tbn->network (-> tbn? network?)]
+               [make-sbn (-> (listof (cons/c variable? tbf/state?)) sbn?)])
  ;; Predicates
  (contract-out [variable? (-> any/c boolean?)]
                [state? (-> any/c boolean?)]
@@ -115,7 +116,8 @@
  (contract-out [state/c contract?]
                [update-function/c contract?]
                [domain-mapping/c contract?]
-               [tbn? contract?]))
+               [tbn? contract?]
+               [sbn? contract?]))
 
 (module+ test
   (require rackunit))
@@ -1249,6 +1251,23 @@
                   (hash 'a (tbf/state '#hash((a . -1)) -1)
                         'b (tbf/state '#hash((a . 1)) 0)))))
 
+;;; A SBN is a network form mapping variables to sbf/state.
+;;;
+;;; The tbf/state must only reference variables appearing in the
+;;; network.  This contract does not check this condition.
+(define sbn? (hash/c variable? sbf/state?))
+
+;;; Builds an SBN from a list of pairs (variable, sbf/state).
+(define make-sbn make-immutable-hash)
+
+(module+ test
+  (test-case "make-sbn"
+    (define sbf1 (make-sbf/state '((a . -1))))
+    (define sbf2 (make-sbf/state '((a . 1))))
+    (check-equal? (make-sbn `((a . ,sbf1) (b . ,sbf2)))
+                  (hash 'a (tbf/state '#hash((a . -1)) 0)
+                        'b (tbf/state '#hash((a . 1)) 0)))))
+
 ;;; Constructs a network from a network form defining a TBN.
 (define (tbn->network tbn)
   (for/hash ([(var tbf) (in-hash tbn)])