Research On Distributed Heterogeneous Data Query Method Based On RDF Metadata

With the development of network and information technology, distributed heterogeneous data query has become increasingly in recent years, and the accuracy and efficiency of query become more and more stringent. Lightweight distributed heterogeneous data integration method has laid a good underlying foundation for the realization of efficient and accurate data query. This method achieves the integration of distributed heterogeneous data through the integration of metadata and ontology. To ensure interoperability and expansibility of metadata, lightweight distributed heterogeneous data integration method adopted the RDF as representation of global metadata. How to retrieve RDF metadata efficiently and accurately and how to query distributed heterogeneous data under the guidance of the metadata is the main contents of this paper. In this paper complete the following work:Firstly, summarize the main problems. First, analyze the problems in the process of distributed heterogeneous data query, summarize existing query processing methods, and discuss the advantages and disadvantages of relevant method. Secondly, review of RDF metadata query method, and analyze the advantages and disadvantages of relevant method.Secondly, the paper proposes a RDF metadata query method. In this method, the index is constructed for RDF metadata firstly. According to the characteristics of RDF data, extract a directed graph and create a path expression from RDF metadata, construct index for path expression using the suffix array and optimize index; Secondly, propose RDF metadata query algorithm on a directed acyclic RDF graph and cyclic.Thirdly, the paper proposes a metadata-based distributed heterogeneous data query method. Query processing method is divided into two phases. The first phase is the query decomposition process. First, construct the global query into a syntax tree based on mediator pattern, then using RDF metadata information tag Wrapper model property in syntax tree, mark the syntax tree that has the same Wrapper model as autonomous tree, and design query decomposition algorithm to traverse the syntax tree and generate subquery. The second phase is the merger process of the subquery result. After subquery returns results, query processor caches the results of the local subquery by block mechanism, eventually merge different subquery results through the join algorithm and return query results to the user. The query processing method can effectively achieve distributed heterogeneous data query and reduce the time of user queries.The proposed methods are verified by experiment and experimental results are satisfactory.