From: Chris Langton (cgl@t13.Lanl.GOV)
Date: Thu May 06 1993 - 15:31:05 UTC
It seems that the fellow who developed turmites and I came up with a similar automaton independently. It's not surprising, really, because its an obvious thing to try. I implemented only one of the possible FSM's mmoving over a 2D tape, while the turmites system allows a wide variety of FSM's to be defined. In principle, these really are Turing Machines, because a TM is just an FSM augmented with an arbitrarily extendable tape. They are interesting for looking at 2D languages, and, for my purposes, for looking at collective phenomena, in which a number of simple agents get caught up in complex dynamics which is mediated by structures in the environment - the agents can modify the environmental structure, while at the same time the same structure is partially determining the agent's behavior. When many agents are modifying and being directed by a shared structure, individual agents can be driven to behave much more complexly than they could in isolation, given the same amount of internal state - a property that has certainly been important in the evolution of social organisms, such as ants, bees, wasps, termites, and even us. My original published account of these automata (which I called "vants" for virtual ants") was in Physica D, V22 pp 120-149 1986. I discuss some extensions of this "virtual automaton" approach in another paper in Complex Ssytems V1 pp 257-271. In the latter paper, I explore the idea that, since the FSM's moving around in the CA are themselves just state configurations, FSM's can write other FSM's on the "tape", which themselves begin to propagate around interacting with both static and other dynamic tape structures (other FSM's). Likewise, such FSM's can read other FSM's because, again, they are simply state configurations on the tape (albeit dynamic ones). They can also modify each other - even erase other FSM's. This all requires that the "rules" for the FSM's be embedded in the CA rules, rather than being externally defined, as in the Turmites system. Nonetheless, I think there are some interesting issues to be pursued in htese kinds of systems. At the Santa Fe Institute, we are building what might be considered a generalization of the Turmites system, in which arbitrarily coded agents propagate around in an environment with its own state and dynamics. Agents can interact with each other and with features of the environment. It is not a CA, although you could simulate a CA within it. It is more in the spirit of Mitch Resnick's *Logo, but more general (agents can be expressed as arbitrary C code, for instance). We are calling this the SWARM simulation system, for obvious reasons. It is now in development, not ready for release, but we should have a beta version within 6 months or so. Cheers! Chris Langton <- cgl@santafe.edu
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