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Artificial life playhouse
Prata S., Waite Group Press, Corte Madera, CA, 1993. Type: Book (9781878739322)
Date Reviewed: Jan 1 1995

Several concepts that fall under the rubric of artificial life, or A-life, are introduced in this nontechnical volume. The book’s central feature is a diskette containing eight programs that demonstrate these concepts. Of the book’s 12 chapters, only 3 (barely more than a third of the text) are a discussion of artificial life. The other chapters are user manuals for the various programs.

Chapter 1, “Artificial Life--What Is It?” discusses two conventional perspectives from which life can be defined: intuitive functional characteristics (such as growth, reproduction, self-maintenance, self-regulation, and metabolism), and the mechanics of conventional life (a cellular architecture relying on carbon-water chemistry and supported by DNA). It then proposes three general principles (the ability to evolve, the dominant role of information, and self-organization) and discusses whether A-life is really alive and how significant it is.

Chapter 2, “A-life Concepts,” introduces basic notions of computation, using finite state machines and cellular automata as examples. It draws a parallel between information processing systems and genetic functions, and discusses basic principles of evolution. Chapter 3, “A-life: Discoveries and Prospects,” highlights some biological insights that have come from A-life experiments and discusses the prospects for practical applications of A-life.

Two examples illustrate how the discussion in these first chapters is disappointingly superficial and often inconsistent. The book’s subtitle implies that evolution is a defining characteristic of life, an implication supported by the author’s listing the ability to evolve as the first of three general principles of life in chapter 1 and by subsequent explicit statements (for example, “Life evolves, and A-life must be able to mimic this feature,” p. 36). Though this important assertion is not defended, many researchers would challenge it. Furthermore, some of the examples of A-life identified and discussed in the book (the Game of Life and lunar robots) do not exhibit evolution.

A second inconsistency is the discussion in chapter 1 of self-organization as the third general principle of life: “Life exhibits some general law of self-organization at work.” The book supports this claim by citing the Miller-Urey experiments, in which electrical discharges in the presence of methane, ammonia, hydrogen, and water yield amino acids. These experiments do show some degree of self-organization, but the connection with Prata’s third principle is not clear, since neither the feedstock nor the resulting amino acids are “alive” in any sense pertinent to Prata’s discussion.

The eight programs discussed in the last two-thirds of the book fall into three categories. Four are cellular automata, including two versions of Conway’s Game of Life. Two show how cumulative selection from random changes, guided step by step by the user, can rapidly yield coherent patterns. The final two programs illustrate genetic evolution in a population of organisms under the pressure of a simulated environment.

The book’s text and the license agreement printed by the publisher at the back of the book directly contradict each other, leaving the reader unclear about the legal status of the example programs. The license agreement permits the user unlimited personal use of the programs but allows only backup copies. The text contradicts both of these claims. First, it identifies several of the programs as either shareware or freeware, available through alternative channels, and even states that readers can copy and distribute some of them. Second, a paragraph on page 59 repeats the standard shareware ethic that readers can continue to use the shareware programs only after paying a registration fee to their authors, above and beyond the purchase price of the book. It is difficult for ethical readers to know what they can and cannot do when the documentation makes contradictory claims.

In sum, the volume offers an elementary introduction to A-life, but its unfortunate inconsistencies may unfairly prejudice readers against this important field.

Reviewer:  H. Van Dyke Parunak Review #: CR118062
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