Basic Explanation of Actors in Erlang

Question

I am trying to put together a very basic explanation of actors in Erlang. It is supposed to be as bare-bones as possible, but without leaving out key features of the theory or the Erlang implementation of it. This is my explanation:

The actor model is a mathematical model of concurrent computation that treats actors as the universal primitives of concurrent computation. The actor is a computational entity that, in response to a message it receives, can concurrently (1) send a finite number of messages to other actors, (2) create a finite number of new actors, and (3) designate the behavior to be used for the next message it receives.

In Erlang, each actor is a separate process in the virtual machine, implemented by a function. Processes communicate by sending messages to each other. Every message is explicit, traceable and safe. The messages are received in a mailbox and stored in the order in which they are received. They are stored there until the receiving process takes them out to be read. This is called asynchronous message passing.

What do you guys think? Is it OK? Should I add or change anything? Thanks.

Answer 1

I think you would help yourself if you didn't confuse actors with Erlang processes. You started with Wikipedia's description of Actor model only to seamlessly start writing about Erlang processes, like if it was one and the same. Actor model is a mathematical model which can be implemented in many different ways, including a pure C or C++ low-level implementation. On the other hand, Erlang processes are lightweight preemptive language features that allow to run a vast amount of processes in parallel much more effectively than it would be possible using native system processes or even threads. It happens that they are modelled after the mathematical model, but it was a design decision based on specific requirements.

I think it would all fit better together if you discussed briefly the Actor model as a mathematical model on its own and only then how it has been implemented in Erlang, pointing out any differences and features specific to Erlang.