Introducing keys and integrity rules in a fuzzy relational data model

This paper discusses the fuzzy functional dependency (FFD), which is considered as integrity constraints and used to define θ-keys. Furthermore, weak/strong θ-entity integrity rules (θ-EIRs) are defined as a result of the extension of classical entity integrity rule, and θ-referential integrity rule (θ-RIR) is defined as a result of the extension of classical referential integrity rule. These results are deemed important, theoretically and practically, both for integrity constraint enforcement and for fuzzy database design