Research On The XML-based Caching In Mobile Database

As in all walks of life a wide range of XML applications,in fact,XML has become a common standard of the data representation and exchange.Therefore,the XML format becomes more and more attractive in the mobile database.However,In the mobile environment,the application of the cache plays a key role in enhancing the performance of the mobile database.Therefore,in the mobile database how to high-performance cache XML database has become a hot research spot.Due to the unique properties of the mobile environment,such as the mobility, frequent disconnection,non-symmetry of the network communications and the limited processing ability of the mobile host and so on.Because the cache in the mobile environment is very different from the traditional cache based on the page,we have to find another smaller granularity than page.In this paper,on the basic of comprehensive analysis the existed XML database cache,in terms of the XML database's property,we proposed a cache granularity and cache stored model in the mobile environment.Under the environment of the mobile database,cache invalidation report can be an effective solution to the cache consistency problems between the server and the mobile client.In this paper,we have discussed two kinds of optimization algorithms based on the traditional cache invalidation report,i.e.XIR algorithm and modified algorithm based on the XIR algorithm.The latter algorithm dynamic adjusts the length of the broadcast interval by the access operation type and access frequency.This modified algorithm can effective improve the performance.Besides,we analysis five types of match model of the semantic cache XML-based and proposed architecture of the semantic cache XML-based and analysis the trimming technology and "Probe Query" and "Reminder Query".Since semantic cache is based on the materialized view,through the "incremental" update the view of the mobile clients,we can avoid unnecessary data transmission and improve the utilization ratio of bandwidth.In order to maintain the view sets in the mobile client more suitably,we have proposed an incremental view updated algorithm, i.e.XS1U.This algorithm introduced the XML nodes' degree and the length of data meta to amend the data freshness.Through simulation analysis,we find that this algorithm can greatly improve the transmission efficiency when the bandwidth declines sharply.