This again sounds extremely like FORTH, with CREATE DOES> giving dynamic runtime behavior. Also, you can override a FORTH word simply by redefining it - you get a helpful "isn't unique" message. The older version will never be found in a dictionary search. If you FORGET the new definition, the old one will be uncovered. This covering I think is a really fundamental idea because it provides a determinate context. You never have to worry about scope because the entire environment is built around scope. Extended FORTH can switch contexts on the fly with VOCABULARY and DEFINITIONS. The root vocabulary is simply called FORTH. Is there an ST analogy?