Research On Skyline Query Technology In Spatial Database

XML is rapidly emerging as the new standard for data representation and exchange on the Internet. It is increasingly common to find operational data and other business information in XML format. In light of the sensitive nature of such business information, this also raises the important issue of securing XML content, and highlights the need for a generic, flexible access control mechanism for XML documents that supports efficient and secure query access, without revealing sensitive information to unauthorized users. On these conditions, this paper analyzes and compares the internal and external researches of XML's access control mechanism, and researches the problem of access control on XML recursive Schema from a new point of view.Firstly, this paper researches the query rewriting approach of access control on security views. Although it can deal with many common queries on security views, there are many limitations, for examples, it cannot rewrite the query on security views. So, this paper introduces query rewrting algorithm on XML recursive security views, analyzes an example of rewrting and takes an experiment. Our experimental results show that the algorithm can effectively rewrites the query on recursive views.Secondly, this paper researches the security-view derivation algorithm. When we analyzed the derivation algorithm, we find that the algorithm cannot deal with the recursive part. So, this paper introduces unfolding recursive nodes algorithm, analyzes an example and takes an experiment to check the correction and feasibility of the algorithm. Our experimental results show that such an unfolding yields a non-recursive(DAG) view DTD that the document is guaranteed to conform to when we use the unfolding algorithm with the recursive nodes in the view derivation process.Finally, the empirical study verifying the feasibility and effectiveness of two approaches which can deal with recursive schema in this paper.