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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 Isolated and heterogeneous database Integrated view needed Solutions Wrapper-Mediator Approach Wrapper Mediator Interface Virtual Database eXtensible Markup Language (XML) Handle data from multiple sources Manage, Store, Query, and Present XML Advantages Data exchange over Internet Representation standard Easy to create with Simple Editor Extensible, Flexible, and Simple System and Vendor Independent Self-Describable 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> DTD <!ELEMENT album (title, song+)> <!ELEMENT title (#PCDATA)> <!ELEMENT song (#PCDATA)> <!ATTRLIST song id CDATA #REQUIRED> 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”> XML Mediator : Architecture Application Application Application Mediator Mediator Mediator Wrapper Wrapper DB1 DB2 Wrapper XML Files XML Mediator : Example Application Retrieve customer names and id Find all Chicago customer names and their order items Mediator Retrieve all cid’s and item names of orders Wrapper Wrapper Customer Database Order Database XML Mediator : Example Application Mediator Wrapper Wrapper Customer Database Order Database XML Mediator : Basic Tasks Database Selection Query Translation Simple Query handled by Wrappers Result Merging Ranking algorithm XML Mediation Systems E-XML Mediator EntireX Mediator E-XML Mediator – System Overview XML Documents XQuery queries e-XML Mediator query SQL query SQL query SQL Wrapper SQL Wrapper RDBMS RDBMS XQuery query Web site Wrapper XDBMS Web site (HTML pages) E-XML Mediator •Administrates the mediator •Registers wrapped data sources Administration Console WWW Client Parser Recomposer Evaluator •Communication interface Metadata Exchanger •Executes query •Gives back the result •Query processing HTTP Applet Gateways Translator Transformer Wrapper Data Source 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 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 EntireX Mediator Architecture