Issues in Designing Disconnected Mobile Database Applications

The design of mobile database applications, which allow uninterrupted disconnected operation, requires the introduction of protocols, which turn mobile hosts into autonomous islands for data management and transaction processing. For this purpose we propose a check-out/check-in mechanism (COCI), which enables transactions to commit on a disconnected mobile host and supports the reintegration of updates when the mobile host can reestablish a connection to the database. At the time of disconnection (check-out, CO), a mobile host reserves integrity constraints to ensure that transactions can commit on a mobile host without asking the database server. At the time of reconnection (check-in, CI), the effects of transactions that committed autonomously on a mobile host need to be integrated to create a semantically correct state of the database. Due to the fact that, at the time being, there is no adequate approach to designing mobile database applications, we briefly analyse the underlying requirements and point out basic alternative design approaches for mobile database applications.