3 A high level view of Goblins

Let’s start with a sketch of a network of Goblins objects wired to communicate with each other:

.----------------------------------.         .----------------------.
|            Machine 1             |         |       Machine 2      |
|            =========             |         |       =========      |
|                                  |         |                      |
| .--------------.  .---------.   .-.       .-.                     |
| |    Vat A     |  |  Vat B  |   |  \______|  \_   .------------.  |
| |  .---.       |  |   .-.   | .-|  /      |  / |  |    Vat C   |  |
| | (Alice)----------->(Bob)----' '-'       '-'  |  |  .---.     |  |
| |  '---'       |  |   '-'   |    |         |   '--->(Carol)    |  |
| |      \       |  '----^----'    |         |      |  '---'     |  |
| |       V      |       |         |         |      |            |  |
| |      .----.  |       |        .-.       .-.     |  .------.  |  |
| |     (Alfred) |       '-------/  |______/  |____---( Carlos ) |  |
| |      '----'  |               \  |      \  |     |  '------'  |  |
| |              |                '-'       '-'     '------------'  |
| '--------------'                 |         |                      |
|                                  |         |                      |
'----------------------------------'         '----------------------'

In the above diagram, we see:

• Two machines (Machine 1 and Machine 2, running separately from each other, but connected to each other over the network via OCapN and CapTP.
• Vat A and Vat B are event loops which live on Machine 1, and Vat C is an event loop which live son Machine 2.
• The individual objects (represented by circles) live in vats, aka event loops which contain objects. Alice and Alfred live in Vat A, Bob lives in Vat B, and Carol and Carlos live on Vat C. (While we’ve given these objects human-like names, they’re just Goblins objects.)
• The arrows between the objects represent references these objects have to each other. Alice has references to both Alfred and Bob. Bob has a reference to Carol. Carlos has a reference to Bob.
• Two objects which are in the same vat are considered near each other, and thus can invoke each other synchronously, whereas any objects not in the same vat are considered far from each other. Any objects can invoke each other by asynchronous message passing… assuming they have a reference to each other.
• Not pictured: each vat has an actormap, an underlying transactional heap used for object communication. This is what permits transactionality and time travel. (Actormaps can also used independently of vats for certain categories of applications.)

Another way to think about this is via the following abstraction nesting dolls:

(machine (vat (actormap {refr: object-behavior})))

• Machines, which are computers on the network, or more realistically, operating system processes, which contain…
• Vats, which are communicating event loops, which contain…
• Actormaps, transactional heaps, which contain…
• A mapping of References to Object Behavior.