interface OperationMessage<P, M extends Map<String, ?>>

Defines the basic format of messages exchanged over domain facade boundary.

Any inbound channel (i.e., web, CLI, messaging, etc.) must convert its accepted messages to this format to be able to send a message into a domain facade.

Metadata is a map containing any non-functional information that must be conveyed from inbound channels into the domain. These might be security-related information, quality-of-service information, metrics and tracing related information, etc. Names of commonly used metadata map keys are enumerated in MetaDataConstant class.

The payload conveys information that might be considered as domain facade's API data structure. Usually, the payload corresponds (at least to some degree) to the data sent by the end-user.