Functional dependencies in extended possibility-based fuzzy relational databases

Based on the fuzzy relational databases where fuzziness of data appears in attribute values in the forms of possibility attributions as well as proximity relations in attribute domain elements, called extended possibility-based fuzzy relational databases, a notion of semantic equivalence of fuzzy data is introduced in this paper. Following this notion, we focus on the issues of fuzzy functional dependencies. A set of sound inference rules, which are similar to Armstrong's axioms (1974) for classical cases, for fuzzy functional dependencies, are proposed.