Message is a data packet that is passed between agents. Messages can model various objects of the real world. For example, they can represent agents – parts, products, people, trucks, etc., or data packets being passed in a network, or commands and signals in a control system.
Messages are instances of arbitrary Java classes. Usually, a message carries some data. To define such a message, you need to define a Java class with necessary member variables and, may be methods. All Java classes you define in your model can be reused in other models as well.
If you need just to signal an object, there is no need in defining new Java class as you can use an instance of the class Object as a message not carrying any data.
Message routing rules