tickNumber = 0;
    public FrameModel() {        tickNumber = 0;        relationshipFrames = new HashSet();        pendingRelationshipFrames = new HashSet();        dataFrames = new HashSet();        allFrames = new HashSet();        graphicsMap = new HashMap();        addedFramesListeners = new ChangeModel();        changedFramesListeners = new ChangeModel();        removedFramesListeners = new ChangeModel();        transitionListeners = new ChangeModel();        graphicChangeListeners = new ChangeModel();        // views        //this.displayWindow = null;        //this.containerView = null;        //this.frameTreeView = null;    }