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The Research And Improvement Of Mapping XML Schema To Relational Schema

Posted on:2008-03-18Degree:MasterType:Thesis
Country:ChinaCandidate:X J HanFull Text:PDF
GTID:2178360212993766Subject:Computer software and theory
Abstract/Summary:PDF Full Text Request
XML is becoming the de facto standard for information publication and exchange on the Web, substituting for HTML. Comparing to HTML, XML is simple, self-describing and the content, structure and representation of XML documents are independent, which makes XML more suitable for data representation and exchange on the Internet. Recently, XML has been widely used in various applications, and very large volumes of XML data have been appeared in the Web. To organize and manage XML data efficiently, different query languages and storage approaches have been proposed. As a viable and promising approach, using RDBMS to manage XML data is extensively studied in recent years.Given that XML databases today are mostly used in web-based query systems where datasets are updated relatively infrequently and the query performance is crucial. Response time is important for web-based query systems where uers tend to.Users want to quicly retrieve the first results. Thus, in our analysis of the schema decompositions we focus primarily on their repercussions on query performance and secondarily on storage space and update speed. But all prior works have been adhered to decomposing XML into high normalized relational schemas, like 3NF or BCNF which convert an XML documents into a typically large number of tuples of different relations. Performance is hurt when a XML document results in a SQL query(or SQL queries)that has to perform a large number of joins to retrieve and reconstruct all the necessary information. Up to now, most of the studies just focus on the structure of XML schema documents, but pay little attention to the constraints of them. These constraints are very important in data integrity,query performance and data completion.In this thesis we focus on XML data storage techniques based on relational databases and the improvement of XML data storage schema, which can improve query performance. After study the related work, an approach to preserving functional dependency (PFD) is presented. Compared with the prior works, PFD takes full advantage of the data dependencies that are implied in XML DTD, and guarantees the integrity of XML documents. The resulting relational schemas keep full functional dependencies and satisty 2NF, which improves the query efficiency.
Keywords/Search Tags:XML, DTD, relational storage, functional dependency, query
PDF Full Text Request
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