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Introduction to Web Applications
Instructor: Enoch E. Damson
Information System
 A collection of components that work together to process
data into accurate information using the information
processing cycle
 Information processing cycle – involves:
 Input
 Processing
 Output
 Storage
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Information System Components
 The main components of an information system are:
 Data – collected data and facts used as inputs for system processing
 Procedures – manual procedures, guidelines, business rules, and
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policies implemented in the system
Hardware – computer systems and devices
Software – applications, operating systems, and any other utilities used
Network – communication infrastructure to connect client processes to
the system
People – users, managers, database administrators, programmers,
systems analysts, systems administrators
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Information System Components…
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Information System Usage
 A collection of components that work together to
process data into accurate information
 Can be categorized based on usage
 Lower-level management – uses information system to
assist management and employees with operational tasks
like inventory systems
 Middle-level management – uses information systems that
deal with midterm goals like forecasting
 Upper-level management – works with information
systems that assist with long-term decision-making goals
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Information System Usage…
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Information System Usage
Categories
 Information systems are classified mainly into the
following distinct categories based on their usage:
 Transaction-processing systems (TPS) – used for
operational tasks like order tracking, customer service,
payroll, etc
 Decision-support systems (DSS) – used for tactical
management tasks like sales forecasting, risk management,
etc
 Expert systems (ES) – captures reasoning of human experts
like loan experts, market analysts, etc
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Architecture
 High-level plan or strategy for building applications
 Can have a number of tiers (usually up to 5 tiers)
 The tiers may place data management, application logic,
and the user interface into separate processes or combine
them in some manner
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One-Tier Architecture
 Combines data management, application logic, and the
user interface into a single executable file
 Many old data processing applications like COBOL
programs use this architecture
 Current desktop (PC) applications like MS Access
applications also use this architecture
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Two-Tier Architecture
 Organizes an application into two layers
 User interface layer
 Data management services layer
 The application/business logic may be in either or both
layers
 Often used in conjunction with client-server computing
which has:
 Clients – sends requests to the server
 Server – manages requests from clients
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Three-Tier Architecture
 Cleanly separates data management, application logic,
and the user interface into different layers
 User interface – manages forms and reports
 Data management – holds the database structure
 Application layer – holds the application logic
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Tiered Architectures
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Types of Applications
 Commonly used types of applications include:
 Client/server applications
 Data warehouse applications
 Web applications
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Client/Server Applications
 Provide a flexible and scalable structure that
 takes advantage of the processing power of personal
computers (PCs)
 utilizes the capacity and power of dedicated servers
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Client/Server Architecture

The typical client/server architecture is made up
of:

Server – providing services to clients
Clients – requesting services from the server

Business Logic – implementing business rules
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Physical Architecture of
Client/Server Applications
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Data Warehouse Applications
 Used in decision-support applications to support executive
management in decision-making processes
 The data warehouse is accessed by software applications or
reporting applications called online analytical processing
(OLAP)
 The OLAP applications retrieve data and generate reports with
the capability of data mining
 Data warehouse – a collection of many types of data taken from
a number of different databases that support various corporate
departments
 Data mining – set of activities used to find new, hidden, or
unexpected patterns in data within a data warehouse
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Physical and Logical Architecture of
Data Warehouse Applications
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Web Applications
 Client/server applications accessed with a Web
browser over a network like the Internet or an
Intranet
 Web applications have become popular because
of the:
 platform-independence of Web browsers and Web
document formats
 ability to update and maintain Web applications
without distributing and installing software on several
client computers
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Web Application Architecture
 Composed of:
 Web browser layer – allows users to navigate through Web
pages on the Internet
 Web server layer – responds to requests submitted by the
Web browsers
 Application server layer – used for data processing and
interfacing to the business logic and database server
 Business Logic layer – implements business rules
 Database server layer – stores and manages data
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Web Application Architecture…
 Uses Web browsers as the front ends
 Uses the Web to communicate with the Web
server
 Uses HTTP as the communication protocol
between the Web browser and the Web server
 Uses HTML/XHTML pages created using,
ActiveX, Java applets, ASP, JSP etc
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Web Application Components
 Logical components of
Web Applications
 Physical structure of
Web Applications
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Examples of Web Applications
 Examples of Web applications include:
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Reservation systems
Weblogs
Massively-Multiplayer Online Role-Playing Game (MMORPG)
Online shopping
Online auction
Games
Multimedia applications
Calendars
Maps
Chat applications
Clocks
Interactive design applications
Stock tickers
Currency converters
Data entry/display systems
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Nature of Web Applications
 Web applications:
 have features and benefits of desktop applications
 have some form of programmatic control either on the
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client side, or on the server, or both
emphasize on real data separation as opposed to
markup/style separation
are usually smaller in file size than desktop applications
can have rich graphical-user interfaces (GUI)
have reduced client-requirements
have portable data
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Building Web Applications
 Two major components needed to build web applications
include:
 Hardware platforms – could be a single shared server
running on a web server and a database
 Software platforms
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Schema – for data storage
Business rule (logic) – for accessing and modifying data
Interactive logic – for presenting data to users
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