Sorry, meant to add the following to my last. As the example above shows, the mep on the service is an implementation detail specific to that service and is used by the pipeline to determine how it should handle requests. The original rosetta code assumed that any message getting to the end of the pipeline was a response and, therefore, sent it whether it was required or not. This lead to duplicate actions (returning messages or nulls), duplicate replies being sent etc. The mep was introduced to control this, providing explicit instruction to the pipeline stating how it should handle any responses. This is nothing to do with a client contract, which we don't really have, and cannot be used to determine client behaviour. Look through the async continuation stuff for more examples of how easy it is to use OneWay services to implement request/response behaviour. Kev View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4238132#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...