Research On Conversion Technology From Relational Schema To XML Based On ER Diagram

With the development of computer and Web technology,more and more information is stored and transmitted by them.On the aspect of information storage the relational database is one of the most mature and the most widely-used technology, while XML provides an excellent intermediate-tool to exchange data.For the application process of using XML as a format of information exchange and management it has become a necessity and a regular behavior to convert the relational-database doucument into XML document.It is of the important value to make research on the transformation from relational data to XML.To put the relational data on the Web is to exchange the flat structure of two-dimensional tables for the hierarchical tree form of XML document.In order to keep the less loss of semantic translation and make the translated XML document to express the original semantics of database well and truly,this paper uses XML Schema that supports a variety of data-types and namespace and has the advantage of expansibility as the final translation form,which improves the limitation of DTD,unable to restrict the internal structure of the text content.Then it adopts the indirect conversion method which extracts ER model from relational table through reverse engineering. With the help of concise and intuitionistic expression of ER model,the unattached tables will be linked by the relationship,which can be reflected.Taking the non-standard factors of database into account at the time of creation this paper puts forward an analytical approach that can check out the correctness of relational semantics and complement the integrality of semantics.It contains functional dependency and inclusion dependency as the two main facors of table semantics and they are supported by the existent theory of SQL query.After the addition of perfect relational semantics based on ER model this method ensures the correctness of semantics and has the unshown one hidden in the table dug up,which provides good semantic source for the next phase of conversion.Next,this paper extends information of the original table. According to the reference relationship between the primary key and the foreign key and the XML Schema-marked template translation rule of entity,attribute of entity and the binary relation type of 1:1,1:n and m:n,the paper lists the conversion arithmetic from relational table to XML Schema and finishes the conversion to XML Schema and proves the correctness of arithmetic in the application and gives the form of XML based on the generated XML Schema.