Grzegorz Rozenberg, a pioneer in the area of natural computing--the area of informatics that studies computational models where computer science and biological processes overlap--is honored in this festschrift.

The papers are organized into eight parts, preceded by an additional part with a single paper, a short professional biography of Rozenberg by Arto Salomaa, one of the editors of the book and a long-time collaborator. Their work together began with Lindenmayer systems (L-systems). Many contributors to the book acknowledge Rozenberg’s early leadership in the area, and his personal and professional collaboration and mentorship. There are a few principal themes running through the book--formal language theory, automata, natural computing, and biochemical reaction systems--areas in which Rozenberg has made major achievements.

The four papers in Part 2, “Sequence Discovery, Generation, and Analysis,” feature DNA, RNA, and protein sequences and their interpretation, by means of formal language theory, grammars, trees, and graph theory. Part 3, “Gene Assembly in Ciliates,” has three papers on the phenomenon of the expansion of the genetic code in the micronucleus of a ciliate (a single-cell creature with two nuclei) when it divides. This behavior is interpreted using formal language theory, string-rewriting operations, and sorting by reversal. Part 4, “Nanoconstructions and Self-Assembly,” has five speculative papers on special geometrical constructions of DNA chains, self-assembly, tiling, and graphs.

Part 5, “Membrane Computing,” has three papers in which the transport of substances across membranes is modeled using formal language theory and P systems. The five papers of Part 6, “Formal Models and Analysis,” include models of very practical applications ranging from splicing DNA segments, the calyx of Held (a region of the brain processing auditory signals), and three papers on biochemistry. The approaches in the papers include formal language theory, &pgr; calculus, Petri nets, probabilistic model checking, and classical biochemical kinetics. Theory dominates in the four papers in Part 7, “Process Calculi and Automata.” The papers are diverse, including modeling biochemistry using stochastic automata and developing from them differential equations for the chemical kinetic processes; process calculus using both &pgr; calculus and differential equations; and using DNA to represent finite automata, leading to massively parallel computation. Part 8, “Biochemical Reactions,” is very unlike conventional biochemistry. The four papers in this section emphasize formal representation of stochastic systems, stochastic reaction networks as a programming language, applying P systems to metabolic processes, and stochastic simulation of a group of cells exchanging molecules through membranes. Part 9, “Broader Perspective,” has the most papers--seven--and the most heterogeneous topics. The topics include Abelian group applications, simulating parallel computing by Xeroxing to transparencies, undecidability in cellular automata, and molecular evolution.

All the papers have lengthy sets of references. Most have a concluding segment in which the authors discuss the open problems remaining in the research they report. This, in itself, is unusual. The discussions of open and unsolved problems are invitations to any reader. There is no master index at the end of the book. The same topic, such as &pgr; calculus, appears in several contributions. Readers need to familiarize themselves with the entire book, in order to find the topic threads on their own. Nevertheless, I recommend this book, created by the editors as a tribute to Grzegorz Rozenberg, for its intellectual breadth and depth.