Message Processing Semantics

Actor Encapsulation

No direct access is possible to the actor behaviour

Only messages can be sent to known addresses (ActorRef)

• every actor knows its own address (self)
• creating an actor returns its address
• addresses can be sent within messages (e.g. sender)

Actors are completely independent agents of compution

• local execution, no notion of global synchronization
• all actors run fully concurrently
• message-passing primitive is one-way communication

Actor-Internal Evaluation Order

Actor is effectively single-threaded.

• messages are received sequentially
• behaviour change is effective before processing the next message
• processing one message is the atomic unit of execution

This has the benefits of synchronized methods, but blocking is replaced by enqueueing a message