III:Next Generation XML Mediators

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Prior research on data integration ledto XML mediators, which provide to applications avirtual integrated XML viewthat allows a single point of access to the data ofmultiple distributed and heterogeneous information sources.Consequent industrial products address Enterprise Information Integrationand follow the Global-As-View paradigm,where the owner specifies the integratedview as an XQuery function of the source views.The emergence of Service-Oriented Architecturesand large scale Internet-based data integration, whichis often needed in the science domains,renders Global-As-View-based information insufficient to benefit fromthe emerging opportunities and inefficient in large scale environments.Service-Oriented Architectures provide live data accessat data sets by offering a set of web service calls to them,as opposed to (the studied in prior works) full query access to the data sets.Large scale data integration highlights the deployment, developmentand maintenance bottleneck that the Global-As-View paradigmcreates by requiring the integrated view owner to have knowledgeof the schema, data formats and semantics of all sources.The proposed mediator provides a scalable solutionby employing a new Global-Local-As-View paradigm in an XML setting:Each source owner can become responsible for fitting her sourcedata and web services to the integrated view.Fundamental algorithmic and system innovations are needed for the implementation of the paradigm.First, queries over the integrated view must be rewritten to use the source services and data. Existing algorithms for rewritingrelational queries over relational views are not sufficient, as they do not address services andthe rich structure of XML queries. Second, the source owner needsan appropriate language and visual tools to export interfaces ina way that can range from full access to theunderlying database to a few parameterized queries and anywhereinbetween. Finally, the client needs corresponding systemsto comprehend which XQueries can be asked on the integrated view.The resolution of the above fundamental contributions will enablethe development of the rewriting module of the UCSD-XMED XQuerymediator, which can become a valuable information sharing and publishing component, especially for science portals where scientists will connect their databases of experimental data to XML-based portals for integrated accessto scientific information. The UCSD-XMED query processor will beused by graduate and undergraduate students in database andmiddleware technologies.Updates about the project, including its people, software distributions and publications are available at http://db.ucsd.edu/NSF07xmlMed/