public void addFrame(Frame frame) {
		if (frame == null) {
			System.err.println("oh no! frame is null");
		}
		String[] idRefParts;
		for (FrameElement fe : frame.getFrameElements()) {
			for (String feID : fe.getIdrefs()) {
				idRefParts = feID.split(":");
				if (!containsNode(idRefParts[0]))
					return;
			}
		}

		for (String targetID : frame.getTargetIDs()) {
			if (!containsNode(targetID))
				return;
		}

		getFrames().add(frame);
	}