A very
powerful feature of the
Smalltalk language, where an
object can have
methods added, removed, overridden, changed, etc. at runtime, rather than at compile-time. In most traditional OO languages (such as
Delphi and
C++) the most
important bits of this can be
faked through
virtual methods and
function pointers, but the
set of available
methods is still
fixed no matter what.
CORBA and COM could do something like this, since they have the infrastructure (querying of an interface before actually calling it) needed.