混合关系中的函数依赖及其相关规则

Functional dependencies and corresponding rules in hybrid relations

在实际应用中有这样一类关系数据库,其中数据项在某个属性上的取值本身又是一个关系。讨论这种混合关系中的函数依赖及其相应的相关规则具有一定的理论意义和实际应用价值。给出这种混合关系的形式定义、混合关系中4种类型的函数依赖关系以及相应的4种类型的相关规则;并给出混合关系到一般关系的转换,通过这个转换说明了混合关系与普通关系的联系及其差别。给出一个实际应用中的例子,来说明混合关系中的函数依赖和相关规则的形式多样性。

In practical applications,there is a class of relations in which the value of a tuple at an attribute is a relation.Such a relation is called a hybrid one.It is necessary to discuss the functional dependences and the corresponding rules in hybrid relations.This paper firstly gives the formal definitions of hybrid relations,and four types of functional dependences and the corre-sponding rules in hybrid relations.Then a transformation from a hybrid relation to a common one is given,the difference between the hybrid relation and a common one is given,and an example is given to show how a hybrid relation is used in a hybrid relation for the graduated student management.