diff --git a/Design:-subflows.md b/Design:-subflows.md
index 3e4a951..22cd518 100644
--- a/Design:-subflows.md
+++ b/Design:-subflows.md
@@ -41,7 +41,28 @@ A subflow can be used in one of two modes: (this is tbd. Might just stick with s
 
 ## Definition
 
-...
+A subflow node has the following properties:
+
+* `type` : `subflow`
+* `id`
+* `name`
+
+A node that is part of a subflow has their `z` property set to the `id` of the subflow.
+
+An instance of a subflow has the following properties:
+
+* `type` : `subflow` ... ?
+* `id`
+* something to identify mode... if we have modes.
+
+It inherits the `name` of the parent subflow.
+
+**Questions:*
+
+* how does an instance node identify its parent?
+    * type=subflow:<parent-id>
+    * type=something other than subflow and parent=<parent-id>
+