Virtual State Machines in Cellular Automata

One of the most important properties of cellular automata is their capacity to support propagating structures. Propagating structures are employed as signals in many CA models of computation. Treating propagating structures as automata elevates the notion of a signal to something that is a computational entity in its own right . These propagating signal-automat a are embedded in th e very "tape" upon which they compute, and are constituted of the very symbols t hat they write on the tape in the course of their computation. Thus, signal-aut omata are both process and data at the same time. They can create, modify, or erase other such automata, and can support distributed computations wherein the operators also serve as operands. As their existence is rather ephemeral when compared to t hat of th e "physical" cells of the lattice that get caught up in their propagat ion, we refer to signal-automata as "vir tual" automata, or virt ual state macb ines (VSM's). In this paper, we look at some examples of VSM sys tems, exp lore a programming methodology based on the process of protein syn thes is, and discuss the implicat ions for "virtual structure" in the physical world.