The developer of such system benefits from using its interactive executable model throughout the whole design cycle. The system under development is represented as a hierarchy of active objects , which are independent, concurrently active, event-driven logical machines. The basic mechanism of object interaction is message passing .
Objects send messages to each other using ports .
Objects may contain other objects to any desired depth. Object replication allows for modeling arbitrary regular structures. Object behavior is described in the form of a Statechart - a state machine extended with state nesting, conditional branching of transitions and history states. Timers are defined graphically as well. The encapsulated objects, ports, states and transitions become its data members.