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On XML Database Query And XML Schema Integration

Posted on:2005-03-14Degree:DoctorType:Dissertation
Country:ChinaCandidate:D Z XuFull Text:PDF
GTID:1118360182468714Subject:Computer application technology
Abstract/Summary:PDF Full Text Request
In current Internet era, overwhelming majority of Web data is still stored in HTML format instead of database. The problem with that is that the Web data have no structure and hence users are not able to have access to Web data via precisely querying them. XML theories and technologies are surging against the situation mentioned above. They provide theoretical and technical support for representing and structuring Web data. Based on what mentioned above, the dissertation does some theoretical and experimental research on abstracting, querying, integrating and optimizing XML data.First, we have established a notion of three-layer model through imitating the process of constructing relational database, which is conceptual, discrete schema and physical layer. Based on the fact that XML file has schema to a certain degree, the dissertation puts forward the concept of discrete schema and hence XML object set, i.e. XML database, is built based on discrete schema. The difference between the three-layer XML model and relational model is that the corresponding XML database is based on discrete schema. Therefore, it is a discrete schema XML database system—DISXDBS. Our research work is to solve various problems around the system by using new ideas and methods.Secondly, after defining a logic language, the dissertation presents the formulaic representation of XML tree model, does research on generic, tree and structural query based on the mathematical schema and represents the integrating query results through using logic expressions. The research above has proved that XML structure can be formulated and provides foundation for graph extension of the tree model.Thirdly, based on the abstract of XML structure mentioned above and in order to improve representation of the XML structure, the dissertation proposes an approach of organizing XML data through graph schema, does research on query in XML context by using graph matching and offers representations and methods of high formality for query. Since we use a discrete schema torepresent a part of XML database, the dissertation represents implementation of query as matching or homomorphism of schema subgraph in XML database based on the mentioned notion of the schema and abstract of XML database (extensible OEM model). It completes graph matching query and implementation of query optimization via using CSP transformation and ensuing solution, which provides a detailed method of transforming discrete schema into CSP and researches and implement on how to solve CSP. Thus, the query in the sense of concrete XML database can be completed. Moreover, the notion and method are used to optimizing query.Fourthly, in order to integrate discrete schema and follow the W3C specification, the dissertation extends XML schema. The extended schema has not only high degree of mathematical representation and also brings in notion of XML algebra and automaton. And the algebra has been proved being a Boolean algebra. A parser which can parse XML documents constrained by the XML algebra is developed. Thus, the idea of integrating discrete schema has been realized. The most significance of the achievement is to have put a theoretical basis for integrating representation of XML documents.Fifthly, the containment with XML features has been defined and been used in optimizing query. The dissertation has done some other theoretical exploration beneficial to optimizing query. The significance is that the existence of difference between optimization of XML query and that of RDB query has theoretically proved. Therefore, it justifies the method used here is reasonable. The dissertation has also done theoretical and experimental research on how to physically store XML data in order to optimize query.Finally, the summary of the research on XML database query and XML schema integration has been made in the dissertation. Also, the plan and the expectation of our future work have been made here.
Keywords/Search Tags:XML schema, database, XML algebra, Match, CSP
PDF Full Text Request
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