PTOLEMY II - CiteSeerX

Actor Libraries
if SDF is the top-level domain, the current time will always be zero, which is likely to lead to some
confusion with timed actors.
4.3 Actor Summaries
In this section, we summarize the actors that are provided in the default Vergil actor library, shown
at the left-hand side of the window in figure 4.2. Note that this library is organized for user convenience,
and the organization does not exactly match the package structure. Here, we give brief descriptions
of each actor to give a high-level view of what actors are available in the library. Refer to the
class documentation for a complete description of these actors (in Vergil, you can right-click on an
icon and select “Get Documentation” to get the detailed documentation for an actor).
It is useful to know some general patterns of behavior:
Unless otherwise stated, actors will read at most one input token from each input channel of each
input port, and will produce at most one output token. No output token is produced unless there are
input tokens.
Unless otherwise stated, actors can operate in all domains except the FSM (finite state machine)
domain, where components are instances of the State class. Additionally, actors that implement the
SequenceActor or TimedActor interfaces may be rejected by some domains.
4.3.1 Sources
A source actor is a source of tokens. Most source actors extend the Source base class, as shown in
figure 4.1. Such actors have a trigger input port, which in some domains serves to stimulate an output.
In the DE (discrete event) domain, for example, an input at the trigger port causes the current value of
the source to be produced at the time stamp of the trigger input. The trigger port is a multiport, mean-
FIGURE 4.2. The default Vergil actor library is shown at the left, expanded to the first level.
130 Ptolemy II