class Node implements Cloneable {

    public String attr(String attributeKey) {
        Validate.notNull(attributeKey);
        if (!hasAttributes())
            return EmptyString;

        String val = attributes().getIgnoreCase(attributeKey);
        if (val.length() > 0)
            return val;
        else if (attributeKey.startsWith("abs:"))
            return absUrl(attributeKey.substring("abs:".length()));
        else return "";
    }

    protected  Node();

}