public Node computeNode() {
      started = true;
      if (isObsolete()) {
        if (LOG.isTraceEnabled()) LOG.debug("obsolete command: ", this);
        return null;
      }
      else {
        if (LOG.isTraceEnabled()) LOG.debug("background command: ", this);
        return computeNode(object);
      }
    }
public Node computeNode()