An important mobile application is to provide users information in a real-time fashion over a mobile network, such asthose for news updates and traffic information. The contents of such information are often highly dynamic, and its validity maychange with time rapidly. It is the best benefit of users if the most recent data can be received by users on time. Informationupdates, which capture the most recent status of interested objects in the external environment, must be done continuously andin a real-time fashion to refresh the values of the corresponding data items in the information servers. However, mobilenetworks are often unreliable, and the available bandwidth is usually very limited. If the rate of information update is too high,the total system workload will be very heavy, and, as a result, the completion times of updates and the validity of many dataitems might be seriously affected. On the other hand, if the update rate is low, the uncertainty level of data validity might behigh, and the external consistency cannot be maintained [1]. In addition to the unreliable mobile network, the mobility ofclients complicates the design of a mobile information system. Queries from mobile clients could have some location-dependent properties. For example, the result of a query might depend on the current location of the originating client. Timingconstraints are often implicitly associated with the processing of queries.In this paper, we introduce a system prototype called