/** @return wheather the entire path is single value */
	function isSingleValue() {
		$prop = $this->getFirstProp();
		if (!$prop ) return null;
		
		$next = $this->getNext();
		if (!$next) return !$prop->isMultiValue();
		
		return !$prop->isMultiValue() && $next->isSingleValue();
	}