The event sourcing philosophy is careful to distinguish between events and commands [48]. When a request from a user first arrives, it is initially a command: at this point it may still fail, for example because some integrity condition is violated. The application must first validate that it can execute the command. If the validation is successful and the command is accepted, it becomes an event, which is durable and immutable.
A message inside an event source system its characterized at first asa command. It defines a user intent but at the moment can still fail. After its validagted it becomes an inmutable event.
