  We model actors based on truly concurrent process algebra, and capture the
actor model in the following characteristics: (1) Concurrency: all actors
execute concurrently; (2) Asynchrony: an actor receives and sends messages
asynchronously; (3) Uniqueness: an actor has a unique name and the associate
unique mail box name; (4) Concentration: an actor focuses on the processing
messages, including some local computations, creations of some new actors, and
sending some messages to other actors; (5) Communication Dependency: the only
way of affecting an actor is sending a message to it; (6) Abstraction: except
for the receiving and sending message, and creating new actors, the local
computations are abstracted; (7) Persistence: an actor does not disappear after
processing a message. Truly concurrent process algebra has rich expressive
ability to model the above characteristics of actors, and more importantly,
they are models for true concurrency, Comparing with other models of actors,
the truly concurrent process algebra based model has the following advantages:
(1) The truly concurrent process algebra has rich expressive abilities to
describe almost all characteristics of actors, especially for asynchronous
communication, actor creation, recursion, abstraction, etc; (2) The truly
concurrent process algebra and actors are all models for true concurrency, and
have inborn intimacy; (3) The truly concurrent process algebra has a firm
semantics foundation and a powerful proof theory, the correctness of an actor
system can be proven easily.
