@SuppressWarnings ("unchecked")
	protected final void append(final BaseItem item) throws NullPointerException, IllegalArgumentException {
		switch (item.state()) {
			case Item.CREATE_STATE:
			case Item.REMOVE_STATE:
			case Item.UPDATE_STATE:
				if (!this.equals(item.pool())) throw new IllegalArgumentException();
				this.doAppend((GItem)item);
			case Item.APPEND_STATE:
				return;
			default:
				throw new IllegalArgumentException();
		}
	}