Research Of Cache Based XML Algebra Querying Optimization

As a kind of semi-structured data, XML has become a standard for data expressing and a language for information exchanging gradually, and it is different from the data models of traditional relational database, so it can not be effectively processed by the traditional database techniques. With the development of XML query language and store mechanism, how to improve the querying efficiency has become more and more important.XML query optimization related to the data storage, the index establishment, the querying language and the algebra expression. Along with the continuous focusing on of the XML query optimization, XML query for caching is gradually gaining more and more attention. The basic idear of improving query time using cache is, caching hot data (frequent query patterns). When a new query requests, DMS(Database management system) first judges whether it can be answered by cache. If it can, the result is returned from cache. In this way, the processing efficiency and response ability can be improved effectively. So, this paper proposed a strategy for query optimization of XML algebra using cache. First, the paper introduced TAX, a kind of query algebra. Expatiated on the pattern tree and witness tree of the query algebra as well as the definition about various operators, explained how to parse XQuery into TAX expression also. Second, this paper explained the query process of XML algebra using semantic cache technology based on this query algebra, and proposed rules of cache matching in the query process. At last, it proved the feasibility and effectiveness of the optimization method according to the result of experiment.