Imagine truly concurrent constraint programming, but without entailment, or any other appeal to logic. In fact, let's try to separate causality from mechanism of specification of interaction.
It may be easier to approach this task from FSM angle, or more precisely, ISM - interacting state machines.
Unlike ISM, our machines (cobs?) do not communicate via FIFO streams of messages - to model causality fairfully, a more rich structure is needed (a cobweb).
Each machine can be thought as crowling along links of immutable network of message nodes, producing another network as its output (to be traversed by other machines). Traversion is not destructive - network nodes not referenced by any machine operatonally are GCed, while denotationally they have infinite lifetime.
FIFO streams are a special case of network with strictly linear links.
To support growth, immutable networks have future nodes (promises) at their frontier - and exactly these nodes are referred (and fulfilled) by the owner machine (hind legs of the cob). Readers of the network cannot get past these growth points (with their front legs) until creator resolves them - a typical future/promise, but probably with more low-level operations than usual.
A machine is a unit of authority, while execution as such can have finer grained units.