The Theory's Research On Normalization Of XML Database

Nowadays, network data exchanging is increasing day by day, as a half- structured data, XML is widely applied in data storage and data transmission fields because of its simplicity, easily marked and running in various platforms. XML database which is sprung up in recent years is a new technology. Like the relational database, the tree structure formed by schema definition may contain data redundancy in the XML data documents, which leads exception in data updating, data inserting and data deleting. The radical reason that brings data redundancy is exception of data dependency, such as partial functional dependency , transitive functional dependency and multiple value dependency.In fact, studying the XML functional dependency plays a fundamental role in other related studies in the XML database technology such as storage and distribution of data, XML data querying and data optimization. Currently, the research on XML functional dependency is focused on strong functional dependency of XML document. The research on weak XML functional dependency—the functional dependency when introducing null in XML tree structure is even seldom.This paper studies the XML data standardization based on the existing DTD rules, according to path expressions and tree component present, the main achievements are listed as follow: 1.The conceptions and inference rules of XML partial functional dependency, transitive functional dependency and multiple value dependency are given, basing on path expressions and tree component.2. Different levels of XML paradigms are defined according to XML formalized definition. It also deduces the XML document standardization rules----element upgrading rules, element establishing rules and element upper moving rules. It gives the XML document standardization algorithm, analyzing the correctness, term- inability, time complexity and nondestructive reliance and maintenance functional dependency of the algorithm .3. It introduces the conception of null in XML tree structure, puts forward XML weak functional dependency containment issue and a set of functional dependency inferences rules suit for XML null model, defines single dependency set, testifies single dependency theorem and single dependency term- inability theorem.