diff --git a/syndicate/assertions.rkt b/syndicate/assertions.rkt
new file mode 100644
index 0000000..c91e42d
--- /dev/null
+++ b/syndicate/assertions.rkt
@@ -0,0 +1,24 @@
+#lang racket/base
+
+(provide message-struct
+         assertion-struct
+         (struct-out observe)
+         (struct-out seal)
+         (struct-out inbound)
+         (struct-out outbound))
+
+;; Thin veneers over `struct` for declaring intent.
+(define-syntax-rule (assertion-struct item ...) (struct item ... #:prefab))
+(define-syntax-rule (message-struct item ...) (struct item ... #:prefab))
+
+(assertion-struct observe (specification))
+
+;; Seals are used by protocols to prevent routing from examining
+;; internal structure of values.
+(struct seal (contents) ;; NB. Neither transparent nor prefab
+  #:methods gen:custom-write
+  [(define (write-proc s port mode)
+     (fprintf port "#{~v}" (seal-contents s)))])
+
+(struct inbound (assertion) #:prefab)
+(struct outbound (assertion) #:prefab)
diff --git a/syndicate/dataspace.rkt b/syndicate/dataspace.rkt
index 2d2d7d6..778122c 100644
--- a/syndicate/dataspace.rkt
+++ b/syndicate/dataspace.rkt
@@ -5,11 +5,6 @@
          with-non-script-context ;; TODO: shouldn't be provided
          run-scripts! ;; TODO: how to cleanly provide this?
 
-         message-struct
-         assertion-struct
-         (struct-out observe)
-         (struct-out seal)
-
          dataspace?
          dataspace-assertions ;; TODO: shouldn't be provided - needed by test.rkt
          generate-id! ;; TODO: shouldn't be provided - inline syntax.rkt??
@@ -66,20 +61,6 @@
 (require "pattern.rkt")
 (require "bag.rkt")
 
-;; TODO: move somewhere sensible
-;; Thin veneers over `struct` for declaring intent.
-(define-syntax-rule (assertion-struct item ...) (struct item ... #:prefab))
-(define-syntax-rule (message-struct item ...) (struct item ... #:prefab))
-
-(assertion-struct observe (specification))
-
-;; Seals are used by protocols to prevent routing from examining
-;; internal structure of values.
-(struct seal (contents) ;; NB. Neither transparent nor prefab
-  #:methods gen:custom-write
-  [(define (write-proc s port mode)
-     (fprintf port "#{~v}" (seal-contents s)))])
-
 ;; An `ActorID` uniquely identifies an actor in a `Dataspace`.
 ;; A `FID` is a Facet ID, uniquely identifying a facet in a `Dataspace`.
 
diff --git a/syndicate/main.rkt b/syndicate/main.rkt
index 0f02183..606cf09 100644
--- a/syndicate/main.rkt
+++ b/syndicate/main.rkt
@@ -1,6 +1,7 @@
 #lang racket/base
 
 (provide (all-from-out "dataspace.rkt")
+         (all-from-out "assertions.rkt")
          (all-from-out "syntax.rkt")
          (all-from-out "ground.rkt")
          (all-from-out "relay.rkt"))
@@ -8,6 +9,7 @@
 (module reader syntax/module-reader imperative-syndicate/lang)
 
 (require "dataspace.rkt")
+(require "assertions.rkt")
 (require "syntax.rkt")
 (require "ground.rkt")
 (require "relay.rkt")
diff --git a/syndicate/relay.rkt b/syndicate/relay.rkt
index 71316d4..62fe108 100644
--- a/syndicate/relay.rkt
+++ b/syndicate/relay.rkt
@@ -11,13 +11,12 @@
 ;; tuples themselves - right?? Oh, maybe observing the observers would
 ;; be an, er, observable difference.)
 
-(provide (struct-out inbound)
-         (struct-out outbound)
-         quit-dataspace!
+(provide quit-dataspace!
          dataspace)
 
 (require racket/match)
 (require racket/set)
+(require "assertions.rkt")
 (require "dataspace.rkt")
 (require "syntax.rkt")
 (require "skeleton.rkt")
@@ -28,9 +27,6 @@
 (require (for-syntax syntax/parse))
 (require "syntax-classes.rkt")
 
-(struct inbound (assertion) #:prefab)
-(struct outbound (assertion) #:prefab)
-
 (struct *quit-dataspace* () #:transparent)
 
 ;; TODO: inbound^n, outbound^n -- protocol/standard-relay, iow
diff --git a/syndicate/skeleton.rkt b/syndicate/skeleton.rkt
index f025204..44eb615 100644
--- a/syndicate/skeleton.rkt
+++ b/syndicate/skeleton.rkt
@@ -18,6 +18,8 @@
 (require racket/list)
 
 (require "bag.rkt")
+(require "pattern.rkt")
+(require "assertions.rkt")
 
 (module+ test (require rackunit))
 
diff --git a/syndicate/syntax.rkt b/syndicate/syntax.rkt
index 1b39580..88b21f3 100644
--- a/syndicate/syntax.rkt
+++ b/syndicate/syntax.rkt
@@ -62,6 +62,7 @@
 (require (for-syntax syntax/srcloc))
 (require "syntax-classes.rkt")
 
+(require "assertions.rkt")
 (require "dataspace.rkt")
 (require (submod "dataspace.rkt" priorities))
 (require "event-expander.rkt")