Research And Application On Query Technology For Continuous Probability XML

In recent years, with the continuous development of data acquisition and processing technology, people’s perception of the data is gradually changing, and data’s attribute is shifting from certainty to uncertainty. In many practical applications, such as Internet, economy, finance and telecommunication, etc. the uncertain data is common and plays a key role. The characteristic of traditional relational database is structural, which is inadequacy for the management of uncertainty in the data. And XML has the advantages of extensibility, flexibility and self-describing, which makes it become the one of data exchange and expression mainstream forms, and also it is particularly suitable for the expression of uncertain data. At present, using continuous probability XML data to manage the uncertain data has been the focus of researchers. and how to develop efficient query methods is the important research objectives.Research content of this article is under the background of a specific project in my graduate. The main content is an improved coding and query algorithm, on the basis of existing XML coding and query technology and the characteristics of continuous probability XML. The content has the following several aspects:In terms of Coding, a new kind of prime coding scheme based on p- document model is proposed in this paper, which is called EPBH(Extended Primes Coding Based on Hierarchy). In practical applications, the XML document will be updated frequently, at present a lot of coding can’t support the update operation well. On the basis of prime number coding, joined the hierarchical relationships, and repeated use of small primes, EPBH coding realizes the support for document update operation. It also avoids the rapid growth of code by prime coding, and is able to determine the structure of the relationship between nodes.In terms of query, a extension twig query algorithm based on EPBH coding is proposed in this paper, which is called PCTwig List. In XML data management, twig query is the core of XML query processing operations, mainly divided into two major categories of merge and non-merge. Twig List is a classic algorithm of merging algorithm based on interval coding.But the shortcoming of Twig List algorithm is in the process of constructing the collection of node list only considering the node relationship between A-D(Ancestor-Descendant), without the relationship between P-C(parent-children), a large number of intermediate results produced in the probability of the XML data query process. In order to improving to solve these problems, PCTwig List algorithm executes three time filtering operation in the course of the entire query, saving time and space and improving the efficiency of the query.In this paper, a large number of comparative experiments is done to prove efficiency of the EPBH coding and PCTwig List algorithm. Finally, the application and implementation of the algorithm in the actual project is introduced.