[carlehewitt]

In a wide-ranging discussion, there were some fundamental disagreements among the panelists as follows:

I disagreed with Tony Hoare about using synchronous communication as the primitive because it is too slow for both IoT and many-core chips. Instead, the primitive for communication should be asynchronous sending and receiving, from which more complex protocols can be constructed.

Also, I disagreed with Tony about sequential actions (using ";") as being foundational. Instead, concurrent actions are foundational for digital systems as follows:

    * Receipt of a communication activated sending other communications
    * An Actor received one communication before it received another communication

Consequently, a computation is a partial order of causality. Tony and I did agree that tooling is needed for navigating the partial order. We just disagreed about whether sequential actions (using ";") are foundational.

Furthermore, class hierarchies are not a suitable foundation for Scalable Intelligent Systems. Interfaces instead of subclassing should be used for IoT communication. Also, entities and descriptions in large ontologies do not fit in an object class hierarchy, e.g., Java and C++. Subclassing is not secure because it allows a subclass to impersonate a superclass.

I disagreed with Joe Armstrong about requiring use of external mailboxes because they are inefficient in both space and time. Instead of requiring an external mailbox for each Actor, buffering/reordering/scheduling should be performed inside an Actor as required.

Of course, Tony and Joe made other great points with which we agree entirely. See the following for more information:

  http://web.stanford.edu/class/ee380/Abstracts/190123.html

[acje]

One of the things I can't see the actor model explain is how to scale an actor vertically, which obviously has it's purpose. Amdahl's law and all that.

However these days we see people build actor frameworks using CSP (golang) and "restricted shared memory" in Rust http://actix.rs

Isn't it ironic? Yet shows that the actor model can be inclusive of many "competing" paradigms, and gain from them, perhaps even need them to scale vertically?

[carlehewitt]

This is a very good question.

Citadels are larger scale Actors which can be incorporated into other Citadels, where a Citadel is an Actor for a systems of Actors (perhaps including IoT).

See the following:

   http://web.stanford.edu/class/ee380/Abstracts/190123.html

[carlehewitt]

Amdahl's law imposes no performance limitation on a system which does not have a sequential part. Having a sequential part is a bad idea because it is a single point of failure.