Semantic Caching for Spatial Mobile Applications

Mobile location-based applications rely heavily on network connections. When the mobile devices are offline, such applications become less accessible to users. A semantic cachebased method is proposed to improve the offline accessibility for mobile location-based applications. The central idea is that when users are browsing information, the client program stores this information for later retrieval. In order to accomplish this on a continuous space, the map projection must be discretized restricting the space to a finite number of windows. On a map window query call, the continuous window is translated into a series of discretized windows which either need to be retrieved from the server or are already stored in the cache. By doing the discretization and caching on the client, no changes must be made to the server allowing it to be easily implemented into most existing applications. An extension of semantic caching allows for prediction based upon past user behavior. The usability of the technique is demonstrated by prototyping it on top the NewsStand system so that the query window is constantly changing as users pan and zoom around the world using a gesturing interface, among others. Evaluation shows the prototype to be effective while decreasing the response time.