Abstract : - Wireless networks have become an integral component of the modern communication infrastructure. Mobile database applications through wireless equipment e.g., PDAs, laptops, cell phones and etc. are growing rapidly. Respect to the limitations in mobile environments, it is strongly recommended to minimize number of connections and volume of data transmission from the servers. Caching data item at the client side is a solution. Moreover, the provision of location-dependent information for the same user at different locations is a challenging problem. In this paper, the performance issues of location-dependent queries is addressed, especially nearest-neighbour search. The system investigates a common scenario where data objects (e.g., restaurants and gas stations) are stationary while users/ clients that issue queries about the data objects are mobile. The grid-partition index is used to answer nearest-neighbour queries directly whereas the area within which the answer is valid can be computed. Moreover, a caching scheme (hybrid and semantic caching) is proposed to record a cache item as well as its valid range.
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