Modifying Software

[Jack Waugh]

I beg the group to forgive a question from someone with no experience
with Self.

My question concerns the effects of modifying a Self image while there
are data in it.

In Smalltalk, you can have a population of instances of some class in
your image, and if you modify the class, the instances change their
behavior accordingly.

Self has no classes, and I suppose most programmnig modification is
done by changing slots in the Lobby or by changing the objects
(usually prototypes) to which those Lobby slots refer.  So in Self,
and in the actual practice of typical Self programmers, and with the
support of typical Self programming environments, is there any way to
modify software so that many existing objects change their behavior to
reflect the modification?