Queries Based On Semantic Cache And Implementation

In mobile computing environment,narrow bandwith,frequent network disconnections and limited client resources have become a challenge of data access.So it is much necessary for client to carry on data caching. Semantic caching is very attractive for use in mobile computing environments. Semantic caching is a caching scheme based on semantic locality among client issued queries.Since semantics about the cached items are stored in semantic caching,the client is able to reason from the local cache to determine whether a query can be totally answered,how much can be answered.Query processing is a key problem in semantic caching. This article studies the mobile environment based on client-side semantic caching of query processing.First of all, introduces the basics of this subject, including the Datalog language, incomplete databases, associative concepts of semantic cache.Secondly, we discuss query processing in several situations, give definitions and determination formula.In order to efficiently use cache to answer queries, We should choose history query which will be cached, give the selection criteria. Based on this data and semantic caching, we discussed several situations of query processing, including the exact match query and cache, including matching, cross matching, disjoint matching. The cross matching is divided into three conditions, namely the level of cross, the vertical cross, mixed cross.Then, we analyse the optimization of query processing .This paper presents a local query processing which can improve the efficiency of query processing approach ,and a answer-completeness determination algorithm which goal is to reduce unnecessary communication. Meanwhile, the optimization also includes reducing the computational complexity of the query optimization of trimming, and query results combination which considered both space and time cost.Finally, research on these issues, designs and implements query processing system based on client-side semantic caching in mobile computing environment. Experimental results show that semantic cache strategy is faster in query response time, effectively reduce the client's network traffic and server visits,and the semantic cache query processing by adding the answer-completeness determination algorithm can be on the appropriate lower response time, reduce network transmission data and the times of servers connecting.