Research Of Active Mechanism For Native XML Databse

XML has grown into a new-generation format of data organization and exchange with the growth of Internet application. Storage and retrieval of XML data in native XML database are realized as two important research areas at this time, and to provide active mechanism for native XML database as for traditional database becomes a hot topic.Active mechanism plays a key role in the implementation of active functionality in active real-time native XML database. The main problems in active mechanism are the definition, storage, and execution of active rules. Based on ARTs-NXD which is an active and real-time native XML database and developed by our research group, research are mainly about the design of active mechanism supporting ARTs-NXD.Devide the events and conditions into five types, thus define active rules described in BNF based on S-A model, and then design some data manipulation and active– rule - management clauses for the AXQuery language based on the current XML query language and then enable ARTs-NXD to support active real-time application.Four primitive types of events and complex events are stored in the event base in a XML element tree style. All triggers stored in the trigger base are cataloged in corresponding events which activate them. The multiple granularity locking method with Intention locks can enhance the concurrency in the event base and the trigger base.The detection of time events includes calculating occur time and set timer. Construct a Finite State Machine to detect complex events. Trigger execution models include Multiple tigger model and nested transaction model. In nested transaction model concurrency control is needed to ensure transaction validity.