Research On Active Rules Based On XML In A Mobile Database

In fact, XML has become a dominant standard for storing and exchanging information with the expanding application fields. The XML format becomes more and more attractive in the mobile database. To introduce active rules into mobile environment can effectively solve many problems arising from mobile database. Therefore, how to carry on the monitoring and analysis to the status of XML documents in the motion environment automatically is also a vital duty.The difference between mobile database and traditional database is not only on events, but also on event detect technology,condition evaluation and conflict detection. In order to introduce active mechanism in mobile database systems, combined with the characteristics of XML, the traditional active rules system should be amended.This paper discusses how to introduce XML-based Active rules in mobile database systems. First based on the ECA rule system model of active database,this paper discuss the knowledge model of XML in mobile database.and describe event,condition action respectively, especially for the events which are different from traditional database. The The events provided new event space for active database and provided effective support for active process of mobile database system. Second, it discusses events detection in mobile database system, and compares the existing method. Third, it discusses composite condition evaluation which based on database conditional transition and mobile condition and its optimization method. It optimizes the condition assessment, combining the method of compute the shortest path of digraph, which can save the bandwidth of mobile network. Finally, discuses the implementation of active rule, in order to reduce the time to searching> matching on rules, in terms of the property of XML, we integrates the rules with the node. The rules are triggered, when have operations on this node. Because each mobile node can do access operations on their own copy of data relatively independent in mobile environments, multiple actions of rules may cause update conflicts of data on mobile node, in order to maintain the consistency of the database, this paper discussed the conflict detection algorithm of rules.