Interface for directors that have a period parameter.
These directors are, by default, untimed, but become timed when
the period parameter is given a value other than 0.0.
The period parameter, if non-zero, specifies the
amount of model time that elapses per iteration.
In this case, the director should fire only at times
that are multiples of the period. If the director is
at the top level, then it is responsible for incrementing time
between iterations. Otherwise, it is responsible for invoking
fireAt() on the enclosing executive director to request
subsequent firings, and refusing to fire (by returning false
from prefire()) at times that are not multiples of the period.
Return true if this director is embedded inside an opaque composite
actor contained by another composite actor. Note that some classes,
such as RunCompositeActor, may return false even if they are actually
embedded, but they want to be treated as if they were not.
True if this directory is embedded inside an opaque composite
actor contained by another composite actor.