1998 Volume 118 Issue 2 Pages 170-179
The effectiveness of artificial life is investigated from an engineering point of view. A system (named S-system) of function-discovery using a bug type of artificial life is proposed in this study. Some functions are extracted by the system. The chromosome of a bug consists of functions, constants and variables. A tree structure is used for the expression of the chromosome. Some observation data are provided for the bugs. After obtaining the data, they reproduce. The concept of sexual/asexual reproduction is introduced in this study. The number of homogeneous bugs is limited for a variety of species. These ideas are very effective for a function-search. A part of the chromosome changes by mutation. As the generation proceeds, the bugs with the function in agreement with the observation data survive selectively, and finally determine the true function. For the validity of this system, some data which obey the known laws have been given for the bugs. The bugs have evolved and discovered some functions in agreement with the laws. As for an unknown function, observation data on glossiness have been provided. They have also discovered the function. In addition, they have determined the multiple curves included in the image data. The S-system has the characteristics that the solution tends to converge and stabilizes in comparison with Genetic Programming. Moreover, the form of the function is relatively simple.