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Paper at a Glance
BibTexStructuring Chromosomes for ContextFree Grammar Evolution Simon Lucas Department of Electronic Systems Engineering University of Essex Colchester CO4 3SQAbstract This paper investigates the use of genetic algorithms for inferring small regular and contextfree grammars. Applied simply, a genetic algorithm is not very ef fective at this. To overcome this problem we invest igate two methods of structuring the chromosomes. The first is to bias the distribution of `1's in the population of chromosomes according to an algeb raic expansion technique previously developed by the author. This `design' of the chromosome distribu tion, shows no bias to any particular type of language (i.e. full generality is retained) yet improves conver gence. The second method involves performing the evolution (i.e. making the mutations) in a different space, where the grammars are represented in `em bedded normal form'. The latter approach structures the chromosome to represent contextfree rather than regular grammars, for example. It is shown that bi asing the chromosome in this fashion produces ex tremely fast convergence, and 3symbol palindromes grammars are learned in typically less than 10 gener ations.
1 Introduction Grammars are an extremely general and useful tool with many applications. These include the higher levels of signal processing, such as pattern recogni tion. However, the application of grammars is limited by the algorithms we can apply to infer them from samples of data. As with many domains, there is a tradeoff between the complexity of a model and the cost of estimat ing it. An example of this may be seen in speech recognition, where hidden Markov models (equival ent to stochastic regular grammars) are applied with great success. These are actually not the most fitting model for speech recognition (for example, contextfree would be a theoretically more appropri ate choice), but due to the existence of fast robust training algorithms, they have ...
@inproceedings{lucas94structuringChromosomes,
author={Simon Lucas},
title={Structuring Chromosomes for Context-free Grammar Evolution},
year={1994},
booktitle={Proceedings of The IEEE Conference on Evolutionary Computation, IEEE World Congress on Computational Intelligence},
url={http://www.isrl.uiuc.edu/~amag/langev/paper/lucas94structuringChromosomes.html}
}
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