public function hasIdentifierPropertiesOnly() {
		if ($this->attributes !== null && $this->attributes->isEmpty() === false) {
			return false;
		}
		if ($this->relationships !== null && $this->relationships->isEmpty() === false) {
			return false;
		}
		if ($this->links !== null && $this->links->isEmpty() === false) {
			return false;
		}
		
		return true;
	}