Answering Query Through Cache During Disconnection
Ting Wu · Chinese Journal of Computers · 2003
Because of the characteristic of wireless networks and mobile units in mobile environments, the mobile computer has to be disconnected often by the user or by accident. During disconnection, clients have no access to networks and can only access information in the local cache. In this paper, we propose a query processing algorithm QPID (Query Processing In Disconnection) based on semantic caches. Semantic cache is a cache that explores the semantic locality among client-issued queries and is composed of former query results and descriptions. In order to provide better support for clients to access data during disconnection and to utilize cache more effectively, QPID algorithm satisfies a query by several cache items. The main idea is to find cache items related to the query first, classify them into direct-related and indirect-related cache items, then process data corresponding to these cache items to get query result. Whether equivalent query answer is obtained is determined by the descriptions of cache items and the query. Experiments show that based on QPID algorithm, semantic cache can be used more effectively and more client queries can be answered during disconnection.