--- a/doc/v2_planning/architecture.txt	Wed Sep 15 10:25:35 2010 -0400
+++ b/doc/v2_planning/architecture.txt	Wed Sep 15 10:48:25 2010 -0400
@@ -57,6 +57,12 @@
 just not essential to choose an API that will guarantee a match, or indeed to
 choose any explicit API at all.
 
+YB: I agree that lambdas are more flexible, but from the user's point of
+view it is really important to know what can swap with what, so that they
+can easily plug-and-play. So even if informal, something in the spirit
+of an API must be described somewhere, and components should declare
+either formally or through comments what functionality 'type' they can take on.
+
 Encapsulation vs. linearity
 ---------------------------