Design patterns·Modelling the domain
the model recorded that the order was placed as a thing that happened, and three unrelated reactions followed.
Domain event
Also calleddomain event pattern, something happened object
An object naming something significant that has occurred in the domain, in the past tense, carrying what happened rather than what to do next. It decouples the thing that changed from everything that must react, and it is how aggregates coordinate without one reaching into another. Making them part of the model — rather than an integration mechanism bolted on later — is what distinguishes this from simply publishing messages.