Type-Reduction of General Type-2 Fuzzy Sets: The Type-1 OWA Approach




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Peer reviewed



For general type-2 fuzzy sets, the defuzzification process is very complex, and the exhaustive direct method of implementing type-reduction is computationally expensive and turns out to be impractical. This has inevitably hindered the development of type-2 fuzzy inferencing systems in real world applications. The present situation will not be expected to change, unless an efficient and fast method of deffuzzifying general type-2 fuzzy sets emerges. Type-1 Ordered Weighted Averaging (OWA) operators have been proposed to aggregate expert uncertain knowledge expressed by type-1 fuzzy sets in decision making. In particular, the recently developed Alpha-Level Approach to type-1 OWA operations has proven to be an effective tool for aggregating uncertain information with uncertain weights in real-time applications because its complexity is of linear order. In this paper, we prove that the mathematical representation of the type-reduced set (TRS) of a general type-2 fuzzy set is equivalent to that of a special case of type-1 OWA operator. This relationship opens up a new way of performing type-reduction of general type-2 fuzzy sets, allowing the use of the Alpha-Level Approach to type-1 OWA operations to compute the TRS of a general type-2 fuzzy set. As a result, a fast and efficient method of computing the centroid of general type-2 fuzzy sets is realised. The experimental results presented here illustrate the effectiveness of this method in conducting type-reduction of different general type-2 fuzzy sets.


Other Research Group involved in the research: CCI


Type-1 OWA operator, Type-2 fuzzy sets, Alpha-level, Type-reduced set, Representation theorem


Chiclana, F. and Zhou, S.M. (2013) Type-Reduction of General Type-2 Fuzzy Sets: The Type-1 OWA Approach. International Journal of Intelligent Systems, 28 (5), pp. 505-522


Research Institute

Institute of Artificial Intelligence (IAI)