Hi--

	So I've been using on-demand behavior transfer to pull into a minimal
snapshot just what's required to run a particular application from a
kitchen-sink snapshot (with a bunch of prerequisites from various
authors). I ran into a situation that made me realize that my approach
wasn't accurate enough.

	What I had been doing was responding to each message not understood by
installing a "loader" method [(RemoteMessageDispatcher
class)>>loadAndResend and friends]. When run, the loader method fetches
the appropriate method from the kitchen-sink system (using a special
network client), then resends the message which originally wasn't
understood. The whole process gets kicked off by a loader method that
represents an entry point for the application in the kitchen-sink
system.

	I got pretty far doing this. New classes were installed and initialized
properly, as a side-effect of transferring method literals. Super-sends
and underrides were handled properly, and transfer loops were avoided.
But I hadn't considered that the possibility of needing an override
before the need for it is detected. In this case, one of the application
classes had an implementation of >>name in the kitchen-sink system, and
an application object in the minimal system sent that message. The
receiver happily ran Object>>name instead of the override; the minimal
system had no way of knowing that it should have installed the
overriding method first.

	This problem seems unsolvable in general (at least, without perfect
type inference, which I am not interested in pursuing). Left unchecked,
it could yield highly subtle errors, and so renders any session
untrustable. So, I've changed my approach to an even more brute-force
one. I'm running the kitchen-sink snapshot in the simulator, and
reporting every simulated send, after the entry point, to another copy
of the kitchen-sink snapshot which is running normally. That snapshot,
in turn, will make sure that the involved method is installed in the
minimal snapshot.

	I appreciate any suggestions or comments. Well, apart from "this is all
nuts"; I've already thought of that one. :)


	thanks,

-C

--
Craig Latta
improvisational musical informaticist
craig at netjam.org
www.netjam.org
[|] Proceed for Truth!