messages.csv:
 - list of message types and their parameters

protocol.csv:
 - list of allowed responses / interactions
 - label + = message can repeat but will be sent at least once
 - label * = message can repeat but can be also completely skipped
 - error message can be sent as a response to any message and terminates the streamlet process
 - warning message can be sent as a response to any message, but does not affect the workflow (just causes e.g. printing a warning to STDERR)