Offline Mechanism Research Of Virtual Experiment Platform

Because Web applications provide good services for users in the offline situation,they become hot issues now. Many well-known companies and institutions have releasedoffline applications on their own products such as Google’s Gmail, Google Doc, andAdobe’s AIR etc. The major use of offline applications’ scripts implemented as browser’splug-ins, having strong platform portability features, but there are still disadvantages suchas not support server and client co-development, not monitor network status immediately,which couldn’t meet the real-time requirements of online virtual experiment platform.Focused on offline applications’ demands of virtual experimental environment, theoffline applications system’s mechanism (VEOAS) is designed and implemented tosupport virtual experiment platform, which solve the problems of saving and runningscenes when network is disconnected. This system contains timing module, which startsfor timing operation when network is disconnected; network monitoring module, whichdetermines the network connectivity of the current situation, in order to confirm that getthe experimental data from servers or local; database access module, which providesdatabase storage and access interfaces to save the experimental data on the local, andoffers data to experiment plug-ins when offline occurs; data exchange module, which isthe middleware of servers and experiment plug-ins, for whom it provides interfaces;server-side caching module, which stores the experimental data on the server-side for dataexchange module when network is disconnected. An Ajax-based monitoring networkasynchronous idea is proposed to solve the problems such as timely detection of thenetwork and get the network status immediately, and it can provide data transparently forusers. Offline applications use server cache technologies to ensure TCP connections, andsend the latest data to client according to users’ session number when the network isconnected again. Offline applications use timestamp to mark experiment data’s replay time,which is used when network is disconnected to ensure the approximate accuracy of data.System tests and results analysis show that offline applications under virtualexperiment platform can save and restore data when the network is broken, show theresults of running, update the latest experimental data to the server, reduce server loadmore than ten percent, and demand bandwidth not exceed ninety percent of the original.