diff --git a/compile.ml b/compile.ml
new file mode 100644
index 0000000..3e26023
--- /dev/null
+++ b/compile.ml
@@ -0,0 +1,22 @@
+open Config
+
+let rec deps_of_zone = function
+  | ZoneIpv4 _ | ZoneIpv6 _ -> []
+  | Zone z -> [z]
+  | ZoneList l -> List.flatten (List.map deps_of_zone l)
+  | ZoneExclude e -> deps_of_zone e
+
+let deps_of_zones zone =
+  List.map (fun (a, b) -> (a, deps_of_zone b)) zone
+
+let compile_zone _ _ = []
+
+let compile_zones zones =
+  let deps = deps_of_zones zones in
+  match Tsort.sort deps with
+  | Tsort.Sorted sorted ->
+    List.fold_right (fun name acc ->
+        let values = List.assoc name zones in
+        let compiled = compile_zone acc values in
+        (name, compiled) :: acc) sorted []
+  | _ -> assert false
diff --git a/dune b/dune
index 80804dc..79a5cb0 100644
--- a/dune
+++ b/dune
@@ -1,3 +1,3 @@
 (executable
  (name firewall)
- (libraries yojson ipaddr))
+ (libraries yojson ipaddr tsort))