Research On The Composite Event Query Optimization Approach For RFID Based On Automata

RFID (radio frequency identification technology) have been widely used in data acquisition and processing of related fields because of its small size, no contact use, high-speed moving object recognition, against harsh environment and other character- istics. With the continuous development of RFID technology, it is found that a comp- osite event formed by basic events according to certain logical connection and pattern matching contains richer information, can support a higher level application of human. Nowadays in the practical application, composite event query is the key technology and becomes a hot topic in the current database.Through studying composite event query technology based on automata, for its shortcomings, this paper proposes the automata representation of composite events including non-temporal composite events and temporal composite events, and gives the optimization approach of multiple composite event processing. The work are as follows。1) According to the equivalence between non-temporal composite event expre- ssons and finite automata, this paper proposes the automata representation of the non-temporal composite events. Considering the shortcomings of the automata in representing the temporal composite events, this paper proposes composite event timed automata model. According to practical application, this paper expands tempo- ral operators. Considering the equivalence between temporal composite event expres- sions and timed automata, this paper proposes the timed automata representation of the temporal composite events.2) This paper proposes the concept of standard query expressions and the sub-query, gives the rewriting steps of composite event queries.3) Considering the the existing composite event query method based on autom- ata is only able to query a single composite event, this paper analyzes the relationship between the various operators, proposes the query sharing approach based on operat- ors and the automata representation of sharing queries. 4) This paper designs a query table to record information of queries and the sharing relationship between them, proposes the table searching-filling method and the largest sub-query searching algorithm, and introduces the query process of sharing queries.The related experiments show that our method can improve the efficiency, reduce implementation cost and response time.