README: Add the milestone about the domains.

README.org

@@ -47,10 +47,22 @@ interaction with Org-mode.
  =build-interaction-graph= to =build-syntactic-interaction-graph=.
     The other functions are somewhat badly structured, somewhat badly
     written, and potentially somewhat wrong.
+
+*** TODO Add variable domains to the network
+    I currently define a network as a mapping from variables to
+    functions, but in fact I very often need the /domains/ of the
+    variables for very many operations.
+
+    I started this transformation a couple of days ago, and decided
+    against it, because I thought that some networks may have
+    unbounded domains.  That's right, but stays hypothetical, while
+    right now I need domains with my networks all the time.
+
 *** TODO Review =build-interaction-graph=
     Check that the definition of this function really follows the
     definition of the interaction graph.  Pay attention to the
     existential vs. universal quantifiers.
+
 *** TODO Start writing the docs properly with Scribble
     Convert some of the comments to Scribble, in particular
     module-level comments introducing the modules and each of