Web Enabled Databases (Web-DB)

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Databases and the Web

An Introduction


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Why is Databases on the

Web Important? Databasesareestablished technology

for managing largeamounts of data

The Web isa good way to presentinformation

Separating data management from

presentation improvesefficiencyupdating

finding information

Credit: Netskills


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Examples of Websites

Using Databases

Organizational information services

employee directories Booking & scheduling

airlines, university coursessignup

Electronic commerce Websiteautomation

www.yahoo.com

www.webmonkey.com


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How to Integrate Databases

and the Web?

Databases

Integration tools


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Databases

Database

an organized collection of data paper-based

DBMS (database management system) software to enable user to create and maintain databases

Relational database

organizes data into tables

RDBMS


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Examples of RDBMS

MS Access

desktop

MySQL, mSQL mid-range

Oracle, Sybase,MS SQL Server

largeenterprise


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How to Integrate Databases

and the Web? Databases

MS Access

MySQL, mSQL Oracle, Sybase,MS SQL Server

Integration tools

PHP or CGI, Servlets, JSP, ASPetc.

Middleware: e.g. ColdFusionhttp://www.allaire.com/


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Application Interface to

Databases CGI

PerlDBI

PerlDBD (DBD::mysql) ASP

ODBC (Open DataBase Connectivity) A standard for the MS world

ODBC driver comes with database MySQL supplies MyODBC

Servlets/JSP JDBC

DBI

DBD::mysql DBD::oracle

CGI


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Relational Databases

Databases that organize data into tables Each tablehas

A name

(For identification)One or more columns

(Forattributes or fields)

Rows

(Forentries or records)


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Relational Database Design

Logical database design

Physical database design


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Logical Database Design

(Entity-relationship modeling)

Identify and model theentities

Identify and model the relationshipsbetween theentities

Identify and model theattributes

Create unique identifier foreachentity

Normalize


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Terminology

Term Definition

Entity A thing (person, place,event,etc.) whichexists

outside of the databaseand is represented in itAttribute Describes the properties ofa particularentity

Relationship Describes theassociationsbetween two or more

entities

Normalization Prevents inefficiency by ensuring no duplicated datain multiple tables


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Physical Database Design

Entitiesbecome tables

Attributesbecome columns

chooseappropriate data type foreachcolumn

Unique identifiersbecome primary keys

Relationshipsare modeled as foreign keys

Foreign keys can be primary keys from othertables


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Structured QueryLanguage (SQL)

Standard language for working with relationaldatabases

a type of naturallanguage

Weare going to useOracle on Borg for theexamples we will do in the class/tutorialsand forassignment-4.

If you want to usesomething else, you are

free to do so. However, note that in thatcase it willbe your responsibility to solveany problems that may come up


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Structured QueryLanguage (SQL)

Standard language for working with relationaldatabases

A type of naturallanguage

You may not have to writeany code Thereare tools for that e.g Accessquery tool

But necessary to understand basics,asSQL is common to all nearly all the toolscovered today


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Two Categories of SQL Statement

1. Data manipulation

SELECT, INSERT,DELETE

2. Data definition

CREATE DATABASE,DROPDATABASE

CREATE TABLE,DROP TABLE


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SQL Statement: INSERT

INSERT INTO table

(col1, col2, col3, ...)

VALUES(text1,text2...,num1,..);

mysql> INSERT INTO employee

-> (firstname, lastname, address,em_id)

-> VALUES(John,Doe,Somewhere,1);


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SQL Statement: DELETE

DELETE FROMtable

WHERE condition;

mysql> DELETE FROM employee

-> WHERE lastname=Jones;


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SQL Statement: SELECT

SELECT column_list

FROMtable

WHERE condition;

mysql> SELECT * from course;

mysql> SELECT description

-> FROM course-> WHERE title LIKE Using%;


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Use SELECT to join tables

SELECT table1.colx, table2.coly...

FROMtable1, table2

WHERE condition;

mysql> SELECT course.title, course.description,

-> teacher.name

-> FROM course, teacher

-> WHERE course.teacher_ID=teacher.teacher_ID;


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Reference

Programming thePerlDBIhttp://www.oreilly.com/catalog/perldbi/chapter/ch04.html


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The EndThe EndThe End


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Aside: Middleware

Adapted from Introduction to Distributed Systems: Slides forCSCI3171 Lectures by E. W. Grundke

References:

[TvS] A. Tanenbaum and M. van SteenDistributed Systems: Principles and Paradigms, Prentice-Hall (2002)

[CDK] G. Coulouris, J. Dollimoreand T. KindbergDistributed System: Concepts and Design, Addison-Wesley (2001)


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LayeredProtocols: IPLayers, interfaces,and protocols in the Internet model.


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LayeredProtocols: OSILayers, interfaces,and protocols in theOSI model.

2-1

7Y6


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Middleware Protocols

An adapted reference model for networkedcommunication.

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7Y6


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Middleware

A softwarelayer that

masks theheterogeneity ofsystems

providesa convenient programming abstraction

provides protocols for providing general-purpose

services to morespecific applications,e.g.

authentication protocols

authorization protocols

distributed commit protocols

distributed locking protocols

high-level communication protocols

remote procedure calls (RPC)

remote method invocation (RMI)


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MiddlewareGeneralstructure ofa distributed system as middleware.

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7Y6


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Middleware and Openness

In an open middleware-based distributed system, the protocols

used by each middlewarelayershould be thesame,as wellas

the interfaces they offer to applications.

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Middleware programming modelsRemote Calls

remoteProcedure Calls (RPC)

distributed objectsand RemoteMethod Invocation (RMI)

e.g. JavaRMI

Common Object Request Broker Architecture (CORBA)

cross-languageRMI

Other programming models remoteevent notification

remote SQL access

distributed transaction processing&'.&K End of Aside

Web Enabled Databases (Web-DB)

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