An activation descriptor contains the information necessary to
activate an object:
the object's group identifier,
the object's fully-qualified class name,
the object's code location (the location of the class), a codebase URL
the object's restart "mode", and,
a "marshalled" object that can contain object specific
An ActivationGroup is responsible for creating new
instances of "activatable" objects in its group, informing its
ActivationMonitor when either: its object's become
active or inactive, or the group as a whole becomes inactive.
The identifier for a registered activation group serves several
identifies the group uniquely within the activation system, and
contains a reference to the group's activation system so that the
group can contact its activation system when necessary.
An UnknownGroupException is thrown by methods of classes and
interfaces in the java.rmi.activation package when the
ActivationGroupID parameter to the method is determined to be
invalid, i.e., not known by the ActivationSystem.