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XML & Mediators

XML & Mediators. Thitima Sirikangwalkul Wai Sum Mong. April 10, 2003. Agenda. Problems and Solutions Introduction to XML XML Mediator Overview XML Mediator Examples. Problems. Problem Storing and Processing Data Efficiently Past Single DBMS Present

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XML & Mediators

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  1. XML & Mediators Thitima Sirikangwalkul Wai Sum Mong April 10, 2003

  2. Agenda • Problems and Solutions • Introduction to XML • XML Mediator Overview • XML Mediator Examples

  3. Problems • Problem • Storing and Processing Data Efficiently • Past • Single DBMS • Present • Isolated and heterogeneous database • Integrated view needed

  4. Solutions • Wrapper-Mediator Approach • Wrapper Interface • Mediator Virtual Database • eXtensible Markup Language (XML) • Handle data from multiple sources • Manage, Store, Query, and Present

  5. XML Advantages • Data exchange over Internet • Representation standard • Easy to create with Simple Editor • Extensible, Flexible, and Simple • System and Vendor Independent • Self-Describable

  6. DTD XML Schema • <xsd:complexType name= “MyAlbum”> • <xsd:sequence> • <xsd:element name= “title” type= “xsd:string”/> • <xsd:element name= “song” type= “xsd:string”/> • </xsd:sequence> • <xsd:attribute name= “id” type= “xsd:string”/> • </xsd:complexType> • <element name= “album” type= “MyAlbum”> <!ELEMENT album (title, song+)> <!ELEMENT title (#PCDATA)> <!ELEMENT song (#PCDATA)> <!ATTRLIST song id CDATA #REQUIRED> Schemas • DTD Vs XML Schema XML Document <album> <title>TITLE A</title> <song id =’1’>song 1</song> <song id =’2’>song 2</song> </album>

  7. XML Mediator : Architecture Application Application Application Mediator Mediator Mediator Wrapper Wrapper Wrapper DB1 DB2 XML Files

  8. XML Mediator : Example Find all Chicago customer names and their order items Application Mediator Retrieve customer names and id Retrieve all cid’s and item names of orders Wrapper Wrapper Customer Database Order Database

  9. XML Mediator : Example Application Mediator Wrapper Wrapper Customer Database Order Database

  10. XML Mediator : Basic Tasks • Database Selection • Query Translation • Simple Query handled by Wrappers • Result Merging • Ranking algorithm

  11. XML Mediation Systems • E-XML Mediator • EntireX Mediator

  12. XML Documents XQuery queries e-XML Mediator query SQL query SQL query XQuery query Web site Wrapper SQL Wrapper SQL Wrapper XDBMS RDBMS RDBMS Web site (HTML pages) E-XML Mediator – System Overview

  13. Administrates the mediator • Registers wrapped data sources • Query processing • Communication interface • Executes query • Gives back the result E-XML Mediator

  14. E-XML Mediator • During query processing, • Determines the sources • Determines the amount of sequential or parallel executions • Determines the amount of query processing that can be offloaded onto the data sources

  15. EntireX Mediator • From Software AG • Acts as a central hub of the XML-based information exchange • Manages XML transactions over Internet • Routes to the receiving application • Converts message to appropriate format

  16. EntireX Mediator Architecture

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