he processing performed by an application on behalf of 
  another application a <em>job</em>.
  There are three different job types:
</p><ul><li> service: must be requested explicitly and includes a message
             sent from the application that perfoms the service (server)
             to the application that requests the service (client).
</li><li> task: must be requested explicitly, but does not include a reply.
</li><li> topic: is sent to registered subscribers without being requested
           ex