The Research Of XML Functional Dependency Based On XML Schema

Nowadays, network data exchanging is increasing day by day, XML, as a half-structured data, is widely applied in data storage and data transmission fields because of its simplicity, easily marked and running in various platforms. XML database is a new technology, which developed in recent years. Just as the relational database, XML data documents may contain data redundancy which caused by a bad designed XML Schema, and containing functional dependency is the basic reason that caused these data redundancies.At present, there are not too much researches on XML functional dependency, the studies based on XML Schema is even seldom. In fact, studying the XML functional dependency plays the fundamental role in other related studies in the XML database technology. This paper studies the XML functional dependency based on the XML Schema, through analysis on the tree structure of XML document and taking advantage of the concept of the tree tuples to substitute the attribute component of relational pattern, propose a formalized definition of XML functional dependency. In additional, this paper infers a inference rules set of functional dependency by using Armstrong axiom-system of database system and testify the inference rules set.This paper defines the transitive functional dependency as well as the indirect functional dependency for XML document, which based on the functional dependency formalized definition of this XML Schema function. This paper also modifies the original XML Schema according to elements establishing rule and upgrading rule, in order to eliminate the indirect functional dependency and the transitive functional dependency, realizes the normalize of XML documents of XML Schema. In the five chapter of this paper, it presents the function containing and covering of XML function, it also educed the smallest functional dependency, and transformed it into the relational pattern, and certified the obtained relational pattern conforming to the requirement of third model requirement.