xml & mediators thitima sirikangwalkul wai sum mong april 10, 2003
TRANSCRIPT
Problems
Problem Storing and Processing Data
Efficiently
Past Single DBMS
Present Isolated and heterogeneous database Integrated view needed
Solutions
Wrapper-Mediator Approach Wrapper Interface Mediator 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
<album><title>TITLE A</title><song id =’1’>song 1</song><song id =’2’>song 2</song></album>
<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 Schema
<!ELEMENT album (title, song+)><!ELEMENT title (#PCDATA)><!ELEMENT song (#PCDATA)><!ATTRLIST song id CDATA #REQUIRED>
DTD
XML Document
XML Mediator : Architecture
Mediator
Application
ApplicationApplication
Mediator
Mediator
DB1 DB2 XML Files
Wrapper Wrapper Wrapper
XML Mediator : Example
Application
Mediator
OrderDatabase
Wrapper Wrapper
Customer Database
Find all Chicago customer names
and their order items
Retrieve all cid’s and
item names of orders
Retrievecustomer names
and id
XML Mediator : Basic Tasks
Database Selection Query Translation Simple Query handled by Wrappers
Result Merging Ranking algorithm
E-XML Mediator – System Overview
XQuery queries
Web siteWrapper
Web site (HTML pages)
SQL Wrapper
SQLWrapper
XQueryquery
SQLquery
SQLquery
XMLDocuments
e-XML Mediator
query
RDBMS RDBMS XDBMS
E-XML Mediator Administration
Console
Evaluator
Parser Recomposer
Exchanger
Metadata
Gateways
Translator Transformer
Wrapper
WWW Client
HTTP
Data Source
Applet
•Administrates the mediator
•Registers wrapped data sources
•Query processing
•Communication interface
•Executes query
•Gives back the result
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 AGActs as a central hub of the XML-based information exchangeManages XML transactions over Internet Routes to the receiving application Converts message to appropriate
format