Modeling and evaluation of prefetching policies for context-aware information services

In a context-aware information service, the service answer depends on the context (e.g. time and location) from which the user issues a query. In a mobile scenario, this impfies that the service must be able to refresh the mswer to a query that is sti~ “active”, when a change in the user context invddates the previously provided answer. In a mobile wireless environment the latency observed by the user before he/she gets up to date information may be high because of the low available bandwidth. A high latency means a long time interti where the user is provided with information not appropriate for his/her context. To r~ duce latency, prefetching techniques are usefti; however, these techniques must be tailored to the pecutiar characteristics of a mobile scenario, where the available bandwidth is quite low, and user devices are typictiy portable computers, with Umited battery fifetime. We propose a general framework to evaluate the effectiveness of prefetching poficies for context-aware information services, and etiuate some of these poficies under different mobifity modeb.

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