Research On The Automatic Generat-ing Technique For XQuery-based Incre-mental Computing Program

In software application field, incremental computation has wide applicablefoundation. However, the development of this kind of computer system is limitedbecause the implementation of incremental computation needs hard algorithm designand tedious software maintenance. Therefore, the implementation of incrementalcomputation needs the support of program automatic generation tools. On the otherhand, as XML is used in data exchange and data sharing on heterogeneousinformation and heterogeneous platform at large, and XQuery is proposed by W3C asthe standard of XML query, more and more applications use XQuery language as themethod to implement XML data query. Therefore, XQuery query optimizingtechnique is a research hotspot nowadays.Our research develops an incremental computation program automatic generationtechnique to perform program transformation for the computation program written inXQuery to generate incremental update program code automatically to obtain newcomputation result according to former computing result, and the executingperformance is better than that of recomputation.At first, our research develops an XQuery based automatic incremental programgenerating method. As a general incremental computation method, it can correspondnot only to XML data modification but also to input data modification. Therefore, thismethod is suitable for querying incremental computation and computationalincremental computation. Besides, the incremental update program is described byXQuery language and can be executed by any free XQuery engine.Secondly, our research presents a bi-directional analysis incremental update codegeneration technique based on the characteristics of XQuery. This technique usesbottom-up modification propagation analysis and top-down program structureanalysis to generate incremental update program. This technique can deal withXQuery computation with conditional expression and user defined functions, and doesnot need the XML data provide index and schema.Thirdly, in order to support incremental update code generation, an XPathmodification region analysis method is developed by our research. This method cancapture a modification region according to XPath expression, the data beforemodification and the modification operation no matter it is an XML data update or aninput data update. This method can support all XPath expression expect "//*" and reverse axis. This method can be used not only for generating incremental updateprogram, but also for incremental maintenance of XPath computation resultindependently.At last, a new XQuery materialized view incremental maintenance system isdeveloped. As a general software tool, it can use the XQuery based automaticincremental program generating method, corresponding the modification of database,maintain the materialized view incrementally and asynchronously. This systemimplies tree-tier framework and is applicable in a distributed system, and an XMLupdate union algorithm and an incremental program union algorithm are used in thissystem to improve the system performance.