Object Data And Xml Data Mapping Rules

XML, as a markup language, has many advantages, such as good extensibility, flexibility and self-description, etc . XML is used widely in the field of Web application and data exchange on the internet. At the same time, XML gives a breakthrough in the coordination between the different platforms, different fields and different applications. Traditional DBMS is a proven technology and is widely used in many data management fields. But now, along with the expansion of information, it face many troubles and challenges. So it' s necessary to join the two technologies together. In this paper, we discuss about these.In the beginning, we give a high-level view about the relation between XML and DBMS. XED and NXD are both major and popular technologies about XML. In this paper, we describe what XED and NXD are, and the differences between XED and NXD. XED is developed from traditional DBMS, which gives module to support the exchange between XML data and traditional data, and has many characteristics about DBMS. NXD is a technology designed specially to deal with XML. Usually, XED is a good choice for data-centric documents, however NXD is suitable to handle document-centric documents.In chapter 4, we discuss the rules about mapping XML to databases, and vice versa. There are two mappings: a table-based mapping and an object-relational (object-based) mapping. Both mappings are commonly used as the basis for software. Table-based mapping is simple, but only works with a very small subset of XML documents. So many applications use the other mapping. Object-based mapping is the most important part in this article. Because XML and object technology is similar in structure, the mapping is based on this. We describe the mapping in the level of simple element, complex element and attributes, and give many examples. In this model, element types with attributes, element content, or mixed content (complex element types) are mapped to classes. Element types with PCDATA-only content (simple element types), attributes, and PCDATA are mapped to scalar properties.In the last part of this paper, based on hierarchical database we give a simple XML data model. In this model, we describe the data types, functions and constraints.