diff --git a/racket/typed/compile-spin.rkt b/racket/typed/compile-spin.rkt
new file mode 100644
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+++ b/racket/typed/compile-spin.rkt
@@ -0,0 +1,36 @@
+#lang racket
+
+(require "proto.rkt")
+
+(module+ test
+  (require rackunit))
+
+;; a SpinProcess is a
+;;   (sproc SName [Listof SVar] [Hashof SName SValue] [Setof SpinState])
+(struct sproc [name vars init states] #:transparent)
+
+;; a SName is a Symbol that is a legal variable name in Spin
+
+;; a SVar is a
+;;   (svar SName SType)
+(struct svar [name ty] #:transparent)
+
+;; a SValue is one of
+;;   - Int
+;;   - Bool
+;;   - SName
+;; and must be a valid Spin literal
+
+;; a SType is one of
+;;  - 'SInt
+;;  - 'SBool
+;;  - 'mtype
+(define SInt 'SInt)
+(define SBool 'SBool)
+(define mtype 'mtype)
+
+;; a SpinState is a
+;;   (sstate SName [Sequenceof SBranch])
+(struct sstate [name branches] #:transparent)
+
+;; a SBranch is a ........