diff --git a/src/todo.txt b/src/todo.txt
index 4b18412..b49d238 100644
--- a/src/todo.txt
+++ b/src/todo.txt
@@ -1,3 +1,6 @@
+- Consider where in Arachne dependency graph is used. If this is only for
+  pruning states, we can construct it there only. However, the base 'role
+  defs/bindings' graph might be re-used.
 - Problem with goal bindings: instantiation of variable with a tuple might
   introduce a tuple goal, which is forbidden. We must find a way to deal with this.
 - For secrecy, one trusted agent and one untrusted agent suffices.