Research On RDF Multi-query Optimization Algorithm Based On Common Substructure

With the rapid development and wide application of Semantic Web technology,the scale of RDF data continues to expand.The massive RDF data set makes the multi-query problem of how to quickly and efficiently return the corresponding result set when multiple users submit query requests at the same time becomes one of the hotspots of current research.The traditional single query optimization mainly improves the efficiency of single query execution from the perspective of the query itself and data processing.It does not take into account that the reusable common parts between multiple queries can reduce the overall computational cost to a greater extent.The time cost of accumulating the sequential execution of multiple individually optimized queries is much higher than the overall execution cost of the query set for multi-query optimization processing.Therefore,compared with single query optimization,multi-query optimization that accelerates high concurrent query processing is of great significance and practical value for solving the problem of slow response of multiple queries.The reuse of common substructures in multiple queries can reduce the overall computational cost,thereby improving the efficiency of multi-query execution.Therefore,this paper proposes two different algorithms for multi-query optimization for the construction,search and reuse of common substructures.The main work is divided into the following aspects: 1)constructing specific RDF data storage indexing mechanism and semantic simplification rules;2)An RDF multi-query optimization algorithm based on triple pattern reordering is proposed and implemented.While constructing common substructures as much as possible,materialized views of valuable common substructures are established to realize reuse;3)An RDF multi-query optimization algorithm based on common substructure for query rewriting is proposed and implemented.The query is rewritten based on the common substructure searched in the query graph,and the rewritten query is re-optimized by the selection rate estimation.In this paper,the comparison between the multi-query optimization algorithm and the commonly used single query optimization method shows that the proposed method has considerable effect on query efficiency.Especially in the case that the RDF data set is large in scale,the number of queries in the query set is large,and the query statement is more complicated,the multi-query optimization method of this paper is better.