An Extended Possibility-Based Fuzzy Nested Relational Database Model and Algebra

Abstract

In order to enhance the expressive power of relational database model, non-first normal (NF2 or nested) relational database model has been introduced, where attribute values may be atomic or set-valued and even relations themselves [1], on one hand. On the other hand, Fuzzy values have been employed to model information imprecision in databases since Zadeh [4] proposed the theory of fuzzy sets. A NF2 relational database model with fuzzy information accommodates imprecision and complexity of the real world objects simultaneously. Based on similarity relation, a fuzzy NF2 relational database model is introduced in [3] and two restructuring operations: Merge and Unmerge are emphatically given. In this paper, an extended possibility-based fuzzy NF2 relational database model is introduced, where the fuzziness of data comes from possibility distributions over universes of discourse and as resemblance relation [2]. We give database model and define fuzzy nested algebra.