- Command:
- Message to change the state of the system.
- Side effects
- System may refuse to act on it
- Query:
- Message to get information from the system
- No side effects.
- System may refuse to answer
- Event:
- message that something changed in some part of the system.
- System may not deny the fact
- System may ignore it.
The message exchange patterns could be request/response or one way ( publish-subscribe, fan in - fan out, push - pull, ...) The message exchange medium can be durable or not ( durable queue , in mem queue, .... )
