A MetaStructure is a higher-level framework treating collections of structures as objects, with natural operations preserving isomorphisms across domains. An Iterated MetaStructure recursively applies MetaStructure construction, forming successive layers where structures of structures create deeper hierarchical meta-levels. In this paper, we define the MetaFuzzy Set, MetaNeutrosophic Set, MetaSoft Set, and MetaRough Set by extending Fuzzy Sets, Neutrosophic Sets, Soft Sets, and Rough Sets through the use of MetaStructure and Iterated MetaStructure.
Takaaki Fujita (Tue,) studied this question.