The Standardization Of The Xml Document

XML (extensible Markup Language) has become one of the primary standards for data exchange and representation on the Internet. It is widely used in various fields. XML documents may contain redundant information and operation anomalies due to a bad designed XML schema DTD which implies the anomaly data dependencies among elements and attributes. This paper studies the normalization problem of XML documents with DTDs as their schemas. This work is composed of three parts as following:1. This part analyzes the differences of functional dependencies when they are applied in XML documents and relational databases respectively. A concept of functional dependency for XML documents based on DTD path expression is proposed. The advantage of this definition is that it can represent the functional dependencies not only between the values of attributes and elements, but also between the nodes of elements. There are two forms of functional dependency: absolute functional dependency and relative functional dependency. And a set of complete inference rules about XML functional dependency is given. Finally, the relation between functional dependency and keys for XML documents are also studied in this part.2. In this part, the concepts of indirect functional dependency and transitive functional dependency for XML documents are proposed. And one XML normal form, XNF-1, is defined based on these concepts. Another XML normal form, XNF-2, is also proposed in this part. The concept of lossless join decomposition for DTDs is also defined by the relational representation of DTDs. Finally, two lossless join decomposition algorithms for transforming an XML document's DTD into XNF-1 and XNF-2 respectively are given.3. XML documents may contain data redundancies and operation anomalies due to non-functional dependencies. The concept of multi-valued dependency for XML documents with DTDs as their schemas is proposed in this part. And another XML normal form, XNF-3, is defined based on the concept of multi-valued dependency. Finally, a lossless join decomposition algorithm for transforming anXML document's DTD into XNF-3 is also given.