Visual Query Interfaces Based On XML Data: The QR_XML System

XML (Extensible Markup Language) consists of four features: flexible data definition format, extensible, highly structure and easily network transmission. Because XML is able to define corresponding tag set for specific application fields, XML can present special project in different systems where there are e-business, government documents, report , publishing and intermediate information etc.. Based on these fields XML documents querying system is becoming important, and the W3C represents XQuery Specifications, for only professional people can use the XQuery engine, one research focuses in the easily-used visual querying system based on Web.In this thesis, we represent data model used by system, relative technique application, query languages translation, and giving one querying system: the QR_XML system, based on XQuery engine. The QR_XML system consists of three components: the QR_XML Web QFRs, the QR_XML Editor, and the QR_XML run-time Engine.Making study of data model, first we investigate XML data model and semi-structure data model. And to research the semi-structure characteristics of XML: self-describe, graph-based model and irregular. Then the analysis of normal tree-structure model is presented. Lastly, we give labeled ordered tree objects. Each internal node of the labeled ordered tree represents an XML element and is labeled with the element' s tag name.The analysis of query set specification QSS(Query set specification) is represented, and QSS is a 4-tuple . Query set specification are used by QR_XML to succinctly encode in QFRs (Query forms and reports) large numbers of possible queries. We build query set specification by the QR_XML Editor, which consists of four processes: building condition tree generator CTG, building result tree generator RTG, defining fragments and dependencies.During the research of the run-time Engine, we investigate the process of condition fragments instantiation, and make parameter instantiation by QSS and user input. Then subtract these improper subtrees by FragmentActivateO algorithm, and build proper minimal active fragments set. In the thesis, the algorithm transforming from the query set specification to the tree query language is represented, and to construct condition tree CT by the set of condition fragments and convert instantiated RTG to result tree RT. Finally,In particular, this paper makes three contributions. First, the easily-used XML data querying system based on Web: QR_XML is represented. Second, data model used by the QR_XML system is represented. Finally, we implement that query set language encodes large numbers of possible queries, the TQL expresses and calculates queries, and the algorithm from QSS to TQL and the one from TQL to XQuery.