a particular connection. These roles are an important
property of the service-elements, so each role is modelled
as an object in the general framework.
The general framework contains three abstract
classes that model the roles of the service-elements:
The abstract-initiator captures the common characteristics
of all initiator objects.
The abstract-responder captures the common characteristics
of all responder objects.
The abstracf-role captures the common properties
of both initiators and responders. It is the superclass
of the abstract-initiator and abstract-responder
classes (see Figure 7)