Bruce Silver's "BPMN: What is a Message? Part 2" continues where the first one stopped, getting into some additional interesting details:
So, to recap, a message must have an addressee, but the meaning of the addressee depends on the target of the message flow:
- Message start event, message is addressed to a process (definition)
- Message intermediate event, boundary event, event subprocess, or Receive task, message is addressed to a specific process instance
- User task, message addressee is not well-defined, but usually a specific process instance
- Black-box pool, message is addressed to an abstract entity, not a process
If you don't fully understand BPMN messages yet, Bruce has you covered.