An optimal construction of invalidation reports for mobile databases

Mobile computing is characterized by frequent disconnection, limited communication capability, narrow bandwidth, etc. Caching can play a vital role in mobile computing by reducing the amount of data transferred. In order to reuse caches after short disconnections, invalidation reports are broadcasted to clients to help update/invalidate their caches. Detailed reports may not be desirable because they can be very long and consume large bandwidth. On the other hand, false invalidations may set in if detailed timing information of updates is not provided in the report. In this research, we aim to reduce the false invalidation rates of the reports. It is found that false invalidation rates are closely related to clients' reconnection patterns (i.e., the distribution of the time spans between disconnections and reconnections). By using Newton's method, we show how a report with a minimal false invalidation rate can be constructed for any given disconnection pattern.