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A survey on universal approximation and its limits in soft computing techniques

delete2003-06-01
delete85
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OA
AI
D
Domonkos Tikk
L
László T. Kóczy
T
T.D. Gedeon
DOI:10.1016/S0888-613X(03)00021-5delete
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Abstract

Abstract

En 中文
This paper deals with the approximation behaviour of soft computing techniques. First, we give a survey of the results of universal approximation theorems achieved so far in various soft computing areas, mainly in fuzzy control and neural networks. We point out that these techniques have common approximation behaviour in the sense that an arbitrary function of a certain set of functions (usually the set of continuous function, C) can be approximated with arbitrary accuracy epsilon on a compact domain. The drawback of these results is that one needs unbounded numbers of building blocks (i.e. fuzzy sets or hidden neurons) to achieve the prescribed epsilon accuracy. If the number of building blocks is restricted, it is proved for some fuzzy systems that the universal approximation property is lost, moreover, the set of controllers with bounded number of rules is nowhere dense in the set of continuous functions. Therefore it is reasonable to make a trade-off between accuracy and the number of the building blocks, by determining the functional relationship between them. We survey this topic by showing the results achieved so far, and its inherent limitations. We point out that approximation rates, or constructive proofs can only be given if some characteristic of smoothness is known about the approximated function. (C) 2003 Elsevier Science Inc. All rights reserved.
Keywords:
universal approximation performed by fuzzy systems and neural networks
Kolmogorov's theorem
approximation behaviour of soft computing techniques
course of dimensionality
nowhere denseness
approximation rates
constructive proofs
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Journal

International Journal of Approximate Reasoning cover
International Journal of Approximate Reasoning
IF:
3
Papers:
2.9K
Citations:
5.1K

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