一种模糊关系代数与模糊关系演算

A Fuzzy Relational Algebra and Fuzzy Relational Calculus

首先给出了模糊数据库的模糊关系数据模型，它允许属性值和元组具有模糊性。在此基础上，构造了两类不同的模糊数据库查询语言：模糊关系代数和模糊关系演算。它们分别以传统的关系代数或关系演算为基础，引入模糊关系（或谓词）、模糊操作（或连接词）和模糊集比较操作。此外，证明了模糊关系代数和模糊关系演算在表达能力上的等价性。模糊关系代数和模糊关系演算既可以作为模糊关系数据模型的理论研究工具，又可作为评价模糊数据库查询语言的准则。

First gives out the fuzzy relational data model of fuzzy database in which the fuzzy values are allowed in both attibute values and tuples. Based on this model, this paper constructs two different kinds of fuzzy database query languages: the fuzzy relational algebra and fuzzy relational calculus. They include the fuzzy relations (or predicates), fuzzy operations (or connectives) and fuzzy set comparison operations based on the classical relational algebra or relational calculus respectively. In addition, this paper proves that the fuzzy relational algebra and fuzzy relational calculus are equivalent in their expressive power each other. The fuzzy relational algebra and fuzzy relational calculus may serve both as tools for theoretical investigations of the fuzzy relational data model, and as criteria for criticizing fuzzy database query languages.