On esb documentation and there's some points(2,3) I didn't understand very well.  Anyone have an exemplo about these itens ?

http://docs.jboss.org/jbossesb/docs/4.9/manuals/html/Programmers_Guide/index.html#d0e3846

   3.2.  The Message

To ensure loose coupling of services and develop SOA     applications, it is necessary to:     

   1.Use one-way message exchanges rather than request-response.

   2.Keep the contract definition within the exchanged messages. Try not to define a service interface that exposed back-end implementation choices, because that will make changing the implementation more difficult later.

   3.Use an extensible message structure for the message payload so that changes to it can be versioned over time, for backward compatibility.

   4.Do not develop fine-grained services: this is not a distributed-object paradigm, which can lead to brittle applications.

Before I read it I would do it (define a service interface that exposed back-end implementation choices). So, how can I do on the right way ?

And about item 3, I really don't understand what that mean ...