We therefore introduce the concept of a message in the next section. This interacting is based on messages which are sent from one object to another asking the recipient to apply a method on itself. Integer presented in section 4.2 . In our pseudo programming language we could create new objects and invoke methods on them. However, in object-orientation there is a view of autonomous objects which communicate with each other by exchanging messages.
Objects react when they receive messages by applying methods on themselves.
They also may deny the execution of a method, for example if the calling object is not allowed to execute the requested method. A message is a request to an object to invoke one of its methods. A message therefore contains the name of the method and the arguments of the method. Consequently, invocation of a method is just a reaction caused by receipt of a message. This is only possible, if the method is actually known to the object.