public SequenceTracker(SequenceSpec spec) {
subObjectives = new ArrayList<ObjectiveTracker>();
for (ObjectiveSpec os : spec.getObjective()) {
subObjectives.add(makeObjectiveTracker(os));
}
current = 0;
accomplished = false;
}
/* observation support (needed for display) */
public void addObserver(EnvironmentObserver o) {
observers.add(o);
}