A reworking of the message oriented model

This diagram represents an attempt to partially refactor the Message 
Oriented Model.

The essential difference here is to bring out that messages have 
originators and ultimate recipients as well as senders and receivers; 
and the structure of the message is closer to the SOAP model.

It also brings out the role of the message transport a little more 
clearly.

Some notes:

1. Originator and ultimate recipient of a message are really 
service-oriented concepts.
2. Correlation is a general concept, that applies elsewhere. The 
general version of this is `counts-as' (as in this message counts as 
the reply to your earlier message).
3. What is not captured here is the idea of a message processing model. 
Is that necessary? It should be covered to some extent in the written 
text

Comments would be welcome