Occurrence getDefaultOccurrence()
    {
        if (default_occurence != null)
            return default_occurence;

        if (parent_queue != null)
            return parent_queue.getDefaultOccurrence();

        return null;
    }
Occurrence getDefaultOccurrence ( ) { if ( default_occurence != null ) return default_occurence ; if ( parent_queue != null ) return parent_queue . getDefaultOccurrence ( ) ; return null ; }
Gets the Queues default Occurrence. Will ask the parent Queue
to get its default Occurrence if this Queue doesn't have one.