XML模式中隐式冗余不存在的充要条件

XML数据库模式规范化设计是产生一组相关联的、能表示数据间依赖关系、而且消除了冗余的XML模式或DTD,以更好地进行信息检索.XML数据库模式中某些数据依赖的存在是冗余存在的原因,因此在XML数据库模式中数据依赖与冗余的关联是其规范化设计研究的关键问题,但对这一问题目前还没有专门的研究.XML数据库模式的数据依赖包括属性间数据依赖和元素间的数据依赖,给出综合了属性间和元素间数据依赖的XML数据库模式数据依赖的定义,分析与之关联的隐式冗余,并论证XML模式中隐式冗余不存在当且仅当该XML模式是规范的,为XML数据库模式规范化设计更深一层的研究奠定理论基础.

The Sufficient and Necessary Condition for No Implicit Redundancies in an XML Schema

XML has emerged as a standard for data representation and interchange on the Internet. Normally the first step for building an XML application is XML database schema design. Normalization design of XML database schema is generating a set of related XML schemas or DTDs that can represent data dependencies and eliminate redundancies, in order to make information retrieval better. The reason why redundancies exist in an XML database schema is that there exist some data dependencies in it. So relationship between data dependencies and redundancies in an XML database schema is a key problem for researches on its normalization design. But there is no research on it now. Data dependencies in an XML database schema consist of data dependencies among attributes and among elements. Data dependencies in an XML database schema by synthesizing data dependencies among attributes and among elements are defined, implicit redundancies relating to it are analyzed, and semi-normal XML schema and normal XML schema are defined based on it. Then the sufficient and necessary condition that no implicit redundancies exist in an XML schema iff the XML schema is normal is proved. This work lays a theoretical foundation for the further research on normalization design of XML database schema.