What is Consistent Database State

An important problem for a database system is to guarantee database consistency. Difficulty arises in devising an efficient algorithm for checking database integrity against updates and for maintaining the consistency of the database, which indisputably desires great attention. However, it is intricate to accomplish particularly in a distributed and mobile environment due to the nature and characteristics of these environments. This chapter presents a model for maintaining the consistency of mobile databases. A rule-based mechanism based on the Event-Condition-Action (ECA) rules is proposed wherein the process of constraint maintenance will trigger the appropriate rule depending on the location (site) where the update is executed. In mobile databases, violation of integrity constraints can occur (detect) at three different levels (locations), namely: mobile host, local base station and remote base station. We believe that the proposed mechanism will reduce the amount of data accessed in addition to the amount of data transferred across the network during the process of maintaining the consistency of the mobile databases. Besides, it is without a doubt that it will speed up the checking process.