Synopsis
Cellular computing is a natural information processing paradigm, capable of modeling various biological, physical and social phenomena, as well as other kinds of complex adaptive systems. The programming of a cellular computer is in many respects similar to the genetic evolution in biology, the result being a proper cell design and a task-specific gene.How should one "program" the cell of a cellular computer such that a dynamic behavior with computational relevance will emerge? What are the "rules" for designing a computationally universal and efficient cell?The answers to those questions can be found in this book. It introduces the relatively new paradigm of the cellular neural network from an original perspective and provides the reader with the guidelines for understanding how such cellular computers can be "programmed" and designed optimally. The book contains numerous practical examples and software simulators, allowing readers to experiment with the various phases of designing cellular computers by themselves.
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1. Introduction 1.1. Emergent computation as a universal phenomena Information exchange is all around us. According to Varela [Varela et al., 1974] life itself is a process of perpetual cognition (or information exchange with the environment). Computer scientists often call information processing and exchange with the word computation, which essentially express the idea of manipulating and transforming information in such a way that is meaningful for a certain purpose or objective. A pragmatic attribute is attached to the meaning of the word "computation" in that we often associate the word not only with the process itself but also with the effective means of achieving it. Therefore, the derived word computer would usually define a medium (electronic, mechanical, bio-chemical, or of other physical nature) used to achieve computation as an emergent property. Starting with the simple abacus, passing trough mechanical computing systems such as Babbage s first computer, until the nowadays digital computers, humans are always in a search for improved and sophisticated computing methods and mediums to satisfy their needs. This process of developing computing machines is a universal and a natural one, which obeys certain life laws according to which life itself is sustained by a continuous information exchange with the external world. It appears that while life itself is the result of a continuous flow of information exchange (or computation in a wider sense), hierarchies of other (superior) "living" entities develop as a result of information exchange between similar entities. So, simple cells collaborate to produce and maintain functional organs, which then are linked in a network forming individuals. Such individuals then form families, villages, countries, federations, etc. Note that in this picture, at a given level of the hierarchy, the actors (let us call them cells) are quite similar and they do usually exchange information only within a very small fraction of the entire population. This particular fraction constitutes a neighborhood, which is essentially of informational nature although some topological constraints may have an influence on which members belong to a neighborhood (for example, a group of scientists usually collaborate through e-mail although they are located geographically at very distances). The same structure is reflected in our brains. Our brain operates as an emergent computer where a network of concepts and relationships are stored. Following the above model, one concept is usually inter-related with only a few other concepts in its neighborhood. Sequentially firing the neurons associated with a mental concept or with a sensorial stimulus will allow the recall of a related concept in several "iterations" corresponding to the same number of neighborhoods activated in the internal network of concepts. A similar hierarchical and cellular organization is revealed in language, which could be considered an "image of our brains". Basic cells (phonemes or characters in the written language) collaborate in an emergent manner to form words, which then are again combined in phrases and so on providing a structured reflection of the outer world. Similar cellular models could be provided for networks of similar electronic circuits, networks of computers and so on. Recapitulating, universal characteristics of our world can be captured in the emergent dynamics of a cellular model where a population of similar cells exchanges information locally with the cells in their neighborhood. Emergent computation depends on how information is exchanged and processed in a cell neighborhood.
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