AtomicStateSystem is a simple system where states consist of single tokens. The rules consist of patterns on the
left that can match these states, and the arbitrary code on the right that creates a new state:
In[] := #["ExpressionsEventsGraph", VertexLabels -> Placed[Automatic, After]] & @
SetReplaceTypeConvert[{WolframModelEvolutionObject, 2}] @
GenerateMultihistory[AtomicStateSystem[{n_ :> n + 1, n_ :> n - 1}],
{"MaxGeneration" -> 4},
None,
EventOrderingFunctions[AtomicStateSystem],
{}] @ 0
Note that spacelike separation is not possible in the AtomicStateSystem. As a result, branching due to overlaps of
different subsets of input tokens cannot occur. And, since events cannot produce branchlike-separated outputs and there
is currently no way to assign multiple outputs to a single match of a left-hand side of a rule, branching can only occur
due to multiple rules.