1. Metadata describes about data. It is ‘data about data’. It has information about how and when, by whom a certain data was collected and the data format. It is essential to understand information that is stored in data warehouses and xml-based web applications.
Data dictionary is a file which consists of the basic definitions of a database. It contains the list of files that are available in the database, number of records in each file, and the information about the fields.
Database is widely used all around the world in differnt sectors: 1. Banking: For customer information, accounts loans and banking transactions. 2. Airlines: For reservations and schedule information. Airlines were among the first to use database in a geographically disturbed manner-terminals situated around the world accessed the central database system through phone lines and other data networks. 3. Universities: For student information, course registrations and grades. 4. Credit card transactions: For purchases on credit cards and generation of monthly statements. 5. Telecommunications: For keeping records of calls made, generating monthly bills, maintaining balances on prepaid calling cards and storing information about the communication networks. 6. Finance: For storing information about holdings, sales and purchase of financial instruments such as stocks and bonds. 7. Sales: For customer, product and purchase information. 8. Manufacturing: For management of supply chain and for tracking production of items in factories, inventories of items in warehouses/stores and orders for items. 9. Human Resources: For information about employees, salaries, payroll taxes and benefits and for generation of paychecks. 10. Web based services:For taking web users feedback,responses,resource sharing etc.
 Effective processing complex data and data with set of the references for expression of the relations between them.
 Building of Internet-shops and distributed information systems.
 Building of the virtual company office and virtual kiosks.
 Storage and reproduction of graphic images, video and audio.
 Creation of WEB-sites, allotted to unlimited opportunities.

2. Web-Database Integration For E-commerce
E-commerce and Databases
What is e-commerce?
Exchanging value electronically (e.g. money for products)
What are typical features of e-commerce site?
 Shop and order online
 Browse and search catalogs
 Track order fulfillment
 Receive personalized information
 Register and track users
 Manage inventory
 Create user communities
Which of these involves using a database?
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Technologies Behind E-commerce
E-commerce requires two key technologies: one old and one new
Databases
 Relational databases devised by Dr. E. F. Dodd in 1970
 Most businesses need databases to be competitive
World-Wide Web (WWW)
 Before the WWW, it was difficult to access databases
 Since the mid-1990's, almost every computer user can access the WWW
 Businesses can reach almost anyone in world to offer products and services
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3. Advantages of Web-Database Integration
 Reduced development costs
o Key is separating content from presentation
o Store information in database or access existing databases
o Create templates to display different categories of information
o Generate web pages automatically using templates and data from database
o More efficient than creating individual web pages and links 'by hand'
 Web site maintenance greatly reduced
o Web pages updated dynamically by changing information in database
o Changing information in database takes less time and skill
 Enhanced web interactivity with personalized information
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E-commerce Architecture
 E-commerce architectures usually consists of three or more tiers
 Multi-tiered approach allows various application to run on different devices
Client Tier
 Browser runs on client machine
 Clients may exist inside or outside firewalls
 Can run applets or applications on client machine
Middle Tier
 Web server responds to user requests with HTML pages
 HTML pages generated from static files or created dynamically by application software
 More applications being connected to servers to provide more services (email, chat, remote login, file transfer, money-transfer, e-commerce)
 Applications sometimes reside on different machines than Web server
 Everything connected by networks
 Middleware is software that mediates between applications and network
Database Tier
 Databases can run on same machine as Web server or on separate machine

4.  Many databases connect through their own server
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Writing Web Applications
 E-commerce sites consist of collection of application programs
 Two main approaches to writing web applications
 Standalone application
o Can create anything computationally possible
o Takes a long time to write or change programs
 Use web-application frameworks
o Collection of generic components providing solutions to number of related problems
o Usually provide scripting languages for interaction between components
 A scripting language is usually:
o weakly typed or untyped
o contains little or no provision for complex data structures
o used to connect components together ("glue")
 Application frameworks often differentiated by their scripting environments
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Web-Application Frameworks/Scripting Environments
Common-Gateway Interface (CGI)
 One of the oldest standards for running external programs on a web server
 Can use any programming language supported by server
 CGI is generally slow because new process created with every call
Active Server Pages (ASP)
 One of the best-known and best-supported web scripting technologies
 Over 1M developers and 35M web pages
 Shipped with most Windows products
 Multi-platform support via Sun's Chilli!Soft product
 Can run many scripting languages including Perl
 Test server speed of 43 pages per second
PHP Hypertext Protocol (PHP)

5.  Open source and works on multiple platforms
 Code is like a mixture of Java, C++ and Perl
 Test server speed of 47 pages per second
Java Server Pages (JSP)
 Part of J2EE framework
 Both open source and commercial versions available
 Embedded Java within HTML pages
 Test server speed of 13 pages per second (Beta 5)
 Probably much faster now with HotSpot JVM
ColdFusion
 In zdnetindia article, rated top choice overall
 Easiest programming language and best administration
 Test server speed of 29 pages per second
For more information
zdnetindia.com: Four scripting languages tried and tested. (circa October 2000)
FAQ's: See the FAQ on this topic.
Links: See the links comparing server-side technologies.
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Comparing Server-side Scripting Languages
Comparison as of 8/15/01
Server-Scripting Language
Industry Usage
ZD Performance
Cost
ASP
63%
43
Yes *
ColdFusion
20%
29
Yes **
PHP
16%
47
Free
JSP
1%
13
Free
* Free on Windows servers, $495 on other servers using Chilli!Soft

6. ** Professional Edition v.5 $1295, Enterprise Edition v.5 $4995, UltraDev Studio v.4.5 $599 (Client only)
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Database Management Systems
 Databases store and manage large collections of information
 Database Management System (DBMS) used to manage databases
 Contains programs to control organization, storage and retrieval of data
 Accepts requests for data and instructs operating system to transfer appropriate data
 Provides security mechanisms to prevent unauthorized users from viewing or updating data
 Maintains integrity by not allowing more than one user to update same record at same time
 Provides mechanisms to interactively enter, update and interrogate data
 Many provide their own Database Server
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Popular DBMS's for Web Sites
 Many DBMS's available to create databases
 Microsoft Access: quite useable for creating low-transaction databases. 100+ simultaneous users if implemented carefully
 Microsoft SQL Server: useful for creating high-transaction databases for busy eCommerce sites
 Oracle: most popular for large organizations due to its extensive capabilities. Can download Oracle9i free for non-commercial use.
 MySQL: becoming popular due to speed, compactness and low cost. Available free under GPL or by low-cost commercial license.
 PostgreSQL: another open source database system
 Scripting languages can access all these databases -- and more
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How Scripting Languages Interface With Databases
 Web-application frameworks provide methods to connect to databases

7.  Most use ODBC, but some provide direct interfaces to specific databases
 ODBC (Open DataBase Connectivity) is open standard for accessing databases using SQL
 SQL (Structured Query Language) is industry-standard language for creating, updating and querying relational DBMS's
 Most DBMS's support ODBC and SQL
 ASP uses ActiveX Data Objects (ADO) and OLE-DB to connect to databases
o ADO is an easy-to-use wrapper for Microsoft's OLE-DB
o OLE-DB is a high-performance, low-level interface to data stores of all kinds
o One of the OLE-DB interfaces connects to ODBC
o Using ADO, ASP can easily access any database with an ODBC driver
 PHP contains modules for connecting to databases and conducting SQL queries
 JSP and Java use Java DataBase Connectivity (JDBC)
o Defines application programming interface (API) for Java
o Uses standard SQL access to databases
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Check Your Understanding
 How can databases make Web sites more dynamic?
 What is the purpose of the middle-tier of the e-commerce architecture?
 Why would a database have its own server?
 What are some of the services that a Database Management System (DBMS) provides to the database?
 What does the Open Database Connectivity (ODBC) standard provide?
 What is Structured Query Language (SQL) used for?