模糊关系数据库的一种广义模型

提出了模糊关系数据库的一种广义数据模型ＧＦＲＤＭ，它是一般模糊关系数据模型的推广，可用来描述现实世界较为普遍的模糊对象。已提出的各种模糊关系数据模型在某种条件下可看作为本模型的特例。文中引入了广义模糊关系的概念，讨论了广义模糊关系代数的操作：广义模糊并、广义模糊交、广义模糊差、广义模糊笛卡尔积、广义模糊投影和广义模糊选择等。广义模糊关系中不仅每一个元组具有模糊性，而且元组的属性值（精确值或模糊值）也具有模糊性（可信度），捕获了更多模糊数据的语义。广义模糊选择操作中允许用户自定义广义模糊比较运算以及指定阈限，从而增强了模糊查询的表达能力和灵活性。

A Generalized Model for Fuzzy Relational Databases

A generalized data model GFRDM for fuzzy relational database is presented. It is a generalization of ordinary fuzzy relational data models and can be used to describe a wide series of fuzzy objects in the real world. A variety of fuzzy relational data models having been proposed can be considered, under certain conditions, as particular cases of this model. This paper introduces the concept of generalized fuzzy relation and extends relational algebra operators such as union, intersection, difference, Cartesian product, selection, projection etc. Every tuple in the generalized fuzzy relation is not only fuzzy, but attribute values (precise or ambiguous) in the tuple are also fuzzy. So the model captures more meaning of fuzzy data. In the generalized fuzzy selection operation, a user may define generalized fuzzy comparators and provide thresholds, hence the expressive power and flexibility of fuzzy queries are enhanced.