private function applyOperations($operations, &$target)
    {
        foreach ($operations as $key => $operation)
        {
            $oldValue = (isset($target[$key]) ? $target[$key] : null);
            $newValue = $operation->_apply($oldValue, $this, $key);
            if (empty($newValue) && !is_array($newValue) && $newValue !== null && !is_scalar($newValue)
            )
            {
                unset($target[$key]);
                unset($this->dataAvailability[$key]);
            } else
            {
                $target[$key] = $newValue;
                $this->dataAvailability[$key] = true;
            }
        }
    }