You've seen how the JCA message-inflow contract can be used to configure a resource adapter so that it can retrieve instances of, and invoke methods on, an MDB.
The contract between a JMS provider and an application server for the delivery of messages to an MDB is now defined in the "Message Inflow" chapter of the JCA specification.
This type of messaging is ideal for processes that may take a long time, such as an application that finds hotel reservations or builds dynamic documents.