The Cache Mechanism Analysis And Applied Research About The G-side Based On G/S Mode

Spatial information network is developing rapidly. When it was displayed in theclient that belongs to the application of spatial information services, it shows thebelow characteristics: complex data types, heterogeneity, large capacity and so on.Inthe field of spatial information, it’s always a hot topic to improve the efficiency ofvisualizing data in the client using caching spatial data.As a spatial network service model,G/S has been widely used in emergencycommand, geo-hazard information preservation and analysis and other industries. Geobrowser, as a platform analyzing and visualizing spatial data, its caching mechanismis the key feature for its data aggregation of client service.The G-side under the G/S modelis a general browser for spatial data visualization,which takes the advantages of the C/S model and B/S model browsers, realizing thedata aggregation of client platform by caching data; which can profoundlyease thepressure of the server for overload by managing, dispatching and storingtwo-dimensional and three-dimensional caching data scientifically.This article describes the importance of cache data for the visualization of data inG-side, concerning the importance of caching technology in the visualization ofspatial data and the limitation and disadvantages in client caching technology dealingwith spatial date. It analyzed and researchedthe specific mechanismorganization ofG-side from the perspective of client services polymerization.Analyze the importanceof the cache data in the client as well as the significance of the data in the client cache,and the characteristics of spatial data, as well as the characteristics and theory of theG-side under G/S model, which set a foundation for the establishment of the generalcache model.Combined the advantages of the general browser applied in spatialinformation network,researched the characteristics of various two-dimensional andthree-dimensional spatial data on purpose, and summarized the advantages and disadvantages of the current cache replacement, and on those bisis established thegeneral cache-model managing and classifying different typed cachedata. Make thisgeneral cache-model asthe core ofthe G-sidecaching mechanism to design the modeland define the main functional interface. The main acheievementexpressed by thepaper is as follows:(1) Designed a general cache model, which is suitable for G-side, and deal withdifferent types of two-dimensional and three-dimensional cache spatial data.Study the method of accessing data, storing data, scheduling cache spatialdata,thesynchronization of cache data in G-side, and the cache mechanism ofreplacingdatathat is failure. Make a classified analysis according to the characteristicsof different types two-dimensional and three-dimensional spatial data. For the specialprocessing data principle of G-side, designed a method to store spatial data based onits type. On this basis,design a general cache model with scalability and versatility, theform of the model, anddefine them by the interface.On the basis of storing andmanaging cache data according to the type, make a cache replacement policycombined to access frequency and storage time of data object.Analyzedifferent cachereplacement methods, and thecompared advantages and disadvantages of them.Designed a cache replacement policy suitable for the characteristics of spatialinformation data, based on the current lack of cachingtechnology and the type ofcache inG-side. According to access frequency, access time and storage time of thecache data, judge the object whether be replaced. The dataset stored cache performedSelf-maintenance functions when the cache is replaced.(2) Defined a full-duplex GSockets connection over which messages can be sentbetween G-side and S-side. Consider it as a core, designed a synchronization moduleof general cache model.Based onthe requirements of thecache synchronization of G-side in the technicalarchitecture of G/S model, designed and realized a communicationprotocol requiredin data synchronizing; analyzed how to keep the data synchronizing between G-sidecache data and S-side data, and the problem of communication access when the datasynchronized, and the importance of communication protocol for data synchronization.For the difference means of communication with the same server between browserand traditional client, designed the full-duplex connection based on GSockets.Consider it as a core, built the initial synchronization module of the general cachemodel.