Reply messages from aggregator

[Sven Bauhan]

Hi,

I'm quite new to Camel and I have a problem to understand the basic 
principle of sending replys back to a sender.
I try to implement a protocol that aggregates segments to a complete 
message. For each segment a reply message is expected by the sender.
My route is now:
        JaxbDataFormat jaxb = new JaxbDataFormat();
        ATSMAggregationStrategy aggregation = new 
ATSMAggregationStrategy();
        from("direct:atsm-segment")
            .unmarshal(jaxb).aggregate(xpath("/MSG/MID"), aggregation)
            .completionPredicate(aggregation).to("direct:atsm-out");

Do I have to set the exchange pattern of the aggregator to InOut? How 
can I do this?
How is the reply message defined? Do I have to set the out message in 
the aggregation strategy?
How do I trigger sending of a reply message?
How is the reply messages routed back to the sender?
Is the reply messages processed automatically (JAXB)?

Thanks,
Sven Bauhan