/**
  * Add object to sequence
  *
  * @param ObjectInterface $object
  */
 public function add(ObjectInterface $object)
 {
     if (!is_integer($object->getScheduledDuration())) {
         throw new \DomainException(sprintf("Missing scheduled duration in '%s' Can't accept object without duration", get_class($object)));
     }
     $this->objects[] = $object;
 }