Complex fuzzy logic

Daniel Ramot*, Menahem Friedman, Gideon Langholz, Abraham Kandel

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


A novel framework for logical reasoning, termed complex fuzzy logic, is presented in this paper. Complex fuzzy logic is a generalization of traditional fuzzy logic, based on complex fuzzy sets. In complex fuzzy logic, inference rules are constructed and "fired" in a manner that closely parallels traditional fuzzy logic. The novelty of complex fuzzy logic is that the sets used in the reasoning process are complex fuzzy sets, characterized by complex-valued membership functions. The range of these membership functions is extended from the traditional fuzzy range of [0,1] to the unit circle in the complex plane, thus providing a method for describing membership in a set in terms of a complex number. Several mathematical properties of complex fuzzy sets, which serve as a basis for the derivation of complex fuzzy logic, are reviewed in this paper. These properties include basic set theoretic operations on complex fuzzy sets - namely complex fuzzy union and intersection, complex fuzzy relations and their composition, and a novel form of set aggregation - vector aggregation. Complex fuzzy logic is designed to maintain the advantages of traditional fuzzy logic, while benefiting from the properties of complex numbers and complex fuzzy sets. The introduction of complex-valued grades of membership to the realm of fuzzy logic generates a framework with unique mathematical properties, and considerable potential for further research and application.

Original languageEnglish
Pages (from-to)450-461
Number of pages12
JournalIEEE Transactions on Fuzzy Systems
Issue number4
StatePublished - Aug 2003


FundersFunder number
University of South Florida Software Testing Center
Space and Naval Warfare Systems Command


    • Complex fuzzy logic
    • Complex fuzzy relations
    • Complex fuzzy sets
    • Complex-valued grades of membership


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