An actor represents an element that is external
to the system. Typical actors that operate on real-time, embedded
systems are buses (for example, Ethernet or MIB), sensors, motors,
and switches.
Actors are a type of UML classifier similar to classes
and they can participate in sequences as instances. However, actors
have the following constraints imposed on them:
- They cannot aggregate or compose any elements.
- They generalize only from other actors.
- They cannot be converted to classes, or vice versa.
IBM® Rational® Rhapsody® can
generate code for an actor, which can be used in simulation testing
of the system you are building.