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Sigrun Ragnarsdottir, March 1999IntroductionXML overviewFigure 1: The markup evolutionFigure 2: The 'X' seriesBenefits from XMLXML VocabulariesXML structureFigure 3: XML structureLogical StructureFigure 4: XML namespacesPhysical StructureXML syntaxFigure 5: Example of a XML document syntaxDatabase Solutions using XMLFlat file SolutionFigure 6: Flat file solutionRelational SolutionsFigure 7: Relational Middle-wareObject Oriented SolutionFigure 8: OO databaseHybrid SolutionFigure 9: Textual databaseVirtual databaseFigure 10: Virtual databaseConclusionsReferencesData storage and delivery on the web and the role of XMLSigrun Ragnarsdottir, March 1999Table of content:Introduction.............................................................................................4XML overview..........................................................................................4Benefits from XML...................................................................................5XML Vocabularies....................................................................................6XML structure.......................................................................................... 7Logical Structure......................................................................................7Physical Structure....................................................................................8XML syntax............................................................................................... 8Database Solutions using XML...............................................................9Flat file Solution.......................................................................................9Relational Solutions................................................................................9Object Oriented Solution.......................................................................11Hybrid Solution......................................................................................11Virtual database.....................................................................................12Conclusions...........................................................................................12References............................................................................................. 12Table of figures:Figure 1: The markup evolution.............................................4Figure 2: The 'X' series..........................................................4Figure 3: XML structure.........................................................4Figure 4: XML namespaces..................................................4Figure 5: Example of a XML document syntax......................4Figure 6: Flat file solution......................................................4Figure 7: Relational Middle-ware...........................................4Figure 8: OO database..........................................................4Figure 9: Textual database....................................................4Figure 10: Virtual database...................................................4IntroductionThe purpose of this survey is to address the role of XML (eXtensible Markup Language) in webtechnology. XML has been put forward as the future markup language of the web. It has simpler syntaxthan SGML and is more expressive than HTML.This survey starts with an overview of XML and then moves into description of how it can be used incombination with different database technology to manage and deliver the data. It addresses several topicslike:- Using XML to access data.- Delivering data using XML.- What kind of storage management to use (flat, OO, Relational, hybrid) and what to store.A lot of companies use relational databases and want to continue using them. Other companies want toexplore new solutions. Each database technology has an effect on performance, storage and flexibility ofthe system. This survey does not take into consideration optimizations for different technologies nor does itconsider different algorithms.XML overviewXML 1997 1992 1986 1960 HTML WWW Internet SGML GM Figure 1: The markup evolutionHTML was created to display data. The need for a relatively simple, flexible and yet powerful ways toexchange, describe and deliver data for the web was needed. The fact that XML is an open standarddeveloped by the W3C ensures that it is uniform and not owned or dominated by any single vendor. Thepower of XML is its separation of view and data, which makes integration of data from diverse sourceseasier.HTML is used to view the data but doesn’t have the flexibility of XML. The attraction to XML is the X(eXtensible). The learning curve for SGML is too high for easy creation of structured or semi-structureddocuments. A lot of work has already been done in SGML, which hopefully is transferable to XMLi.XML document XSL/CSS Style-sheet Formatted document Resource XLL Linking language Resource Figure 2: The 'X' seriesTo explore XML beyond using it as a data format we have to mention three related, but different standards:- XML (eXtensible Markup Language). Describing the markup standard. Structured data inXML can be self-describing with either DTD (Document Type Definition) or with XML-Schemas. They provide a description of the structure of the data, if it doesn’t already havea built in description.- XSL (XML Style-sheet Language, eXtensible Style Language). Describing how thearbitrary tags of an XML document should be presented under certain rules; they can hidesome elements and display others. XSL provides a superset of CSS (Cascading StyleSheets).- XLL (eXtensible Linking Language). Describes how to link from a linking element to aresource. XLL takes HTML linking a bit further and is divided into Xlinks for linking andXpointers for addressing individual parts and/or range or spans of a document.In addition, several standards for exchange of meta-data have been suggested, like by Microsoft (XML-Data), Netscape (MCF) and W3C (RDF).As a reference for XML I looked at Microsoft’s web siteii, got declarations from OASISiii and books byHaroldiv and Bradleyv.Benefits from XMLXML will contribute most for the following situationsvi:- Virtual databases, where the client has to mediate between two or more heterogeneousdatabases. XML can use vocabularies to add meta-data or meta-content to HTML makingdata exchange easier.- Applications that try to move the workload from


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CORNELL CS 632 - Study Notes

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