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SE 341 Web Application Development

Lecture 2

SPRING 2009

Muneera BanoAssistant Professor DCS, FBAS, IIU

muneera@iiu.edu.pk

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Basic Concepts

Communication

It is any transmission, emission, or reception of

signs, signals, writings, images and sounds or

intelligence of any nature by wire, radio, optical or

other electromagnetic system.

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Basic Concepts

Communication

A communication model comprises of following

subsystems:

Source Generates the data to be transmitted

Transmitter Converts the data into transmittable

signals

Transmission system Carries the data.

Receiver Converts received signals into data.

Destination Takes incoming data.

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Basic Concepts

Data and Computer Communication

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Basic Concepts

Computer Networks

A network is a collection of computers and devices

connected to each other.

The network allows computers to communicate

with each other and share resources and

information.

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Basic Concepts

Network Model

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Basic Concepts

World Wide Web

The World Wide Web (commonly abbreviated as "the

Web") is a system of interlinked hypertext documents

accessed via the Internet.

With a Web browser, one can view Web pages that

may contain text, images, videos, and othermultimedia and navigate between them using

hyperlinks.

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Basic Concepts

World Wide Web

Viewing a Web page on the World Wide Web normally begins either by typing the

URL of the page into a Web browser, or by following a hyperlink to that page or

resource.

The Web browser then initiates a series of communication messages, behind the

scenes, in order to fetch and display it.

First, the server-name portion of the URL is resolved into an IP address using the

global, distributed Internet database known as the domain name system, or DNS.

This IP address is necessary to contact and send data packets to the Web server.

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Basic Concepts

URL (Uniform Resource Locator)

In computing, a Uniform Resource Locator (URL) is a

type of Uniform Resource Identifier (URI) that

specifies where an identified resource is available and

the mechanism for retrieving it.

In popular language, a URL is also referred to as a Webaddress.

E.g. http://www.yahoo.com

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Basic Concepts

DNS (DomainName Server)

A name server (also called 'nameserver') consists of a

program or computer server that implements a

name-service protocol.

It will normally map (i.e. connect) a human-

recognizable identifier of a host (for example, the

domain name 'en.wikipedia.org') to its computer-

recognizable identifier (such as the Internet Protocol

(IP) address 145.97.39.155), and vice versa

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Basic Concepts

IP Address

An Internet Protocol (IP) address is a numerical

identification (logical address) that is assignedto

devices participating in a computer network utilizing

the Internet Protocol for communication between its

nodes.

The role of the IP address has been characterized as

follows: "A name indicates what we seek. An address

indicates where it is. A route indicates how to get

there."

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Basic Concepts

Web Clients and Web Browsers

A Web browser is a software application which enables a user to display

and interact with text, images, videos, music, games and other

information typically located on a Web page at a Web site on the World

Wide Web or a local area network. Text and images on a Web page can contain hyperlinks to other Web pages

at the same or different Web site.

Web browsers allow a user to quickly and easily access information

provided on many Web pages at many Web sites by traversing these links.

Web browsers format HTML information for display, so the appearance ofa Web page may differ between browsers.

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Basic Concepts

Web Servers

Web servers are able to map the path component

of a Uniform Resource Locator (URL) into:

a local file system resource (for static requests);

an internal or external program name (for dynamic

requests).

For a static requestthe URL path specified by theclient is relative to the Web server's root directory.

E.g IIS for Windows XP

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Basic Concepts

Working of the WEB

First, the server-name portion of the URL is resolved into an IP address

using the global, distributed Internet database known as the domain name

system, or DNS.

This IP address is necessary to contact and send data packets to the Webserver.

The browser then requests the resource by sending an HTTP request to

the Web server at that particular address.

In the case of a typical Web page, the HTML text of the page is requested

first and parsed immediately by the Web browser, which will then makeadditional requests for images and any other files that form a part of the

page.

Having received the required files from the Web server, the browser then

renders the page onto the screen as specified by its HTML, CSS, and other

Web languages

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Basic Concepts

Protocols It is a set of rules governing the format and meaning

of frames, packets, or messages that are exchanged bypeer entities within a layer.

Protocol are used for communications betweenentities in a systems.

Entities use protocols in order to implement theirservice definitions.

The key elements of a protocol are: Syntax : Include Time data formats and signal levels

Semantics: Includes control information and errorhandling.

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Basic Concepts

HTTP (Hyper Text Transfer Protocol)

HTTP is an application level protocol for

communication over WWW.

HTTP Request

HTTP Response

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Basic Concepts

Web Pages / Web Sites / Web Application

Web page is a document stored on web servers

directory.

Web site is collection of web pages interconnected

through hyperlinks.

Web application is a software system to be accessed

over internet through web protocols.

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Basic Concepts

Static and Dynamic Web Sites

Static web pages have predefined contents and

predefined behavior prior to execution by web

server.

Dynamic web pages, will define their contents and

behavior after execution from web server.

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Basic Concepts

Client Side Scripting

Coding in which web server may not be required.

Web Browser/ Web Client can execute the

instructions.

Static web pages are almost all coded in client side

scripting.

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Basic Concepts

Server Side Scripting

Web Server is required to execute the

instructions.

Web browser will only display results from web

server.

Dynamic web pages are mostly coded in server

side scripting.

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Basic Concepts

Web Services

A software application identified by URI in distributed

environment.

They can be discovered and utilized based on user

requirements.

It is evolution to web 2.0 from traditional web pages

of web 1.0

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Basic Concepts

WSDL (Web Service Description Language)

Used for registering and Discovery of web services

over internet.

Used to describe the behavior of web service.

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Basic Concepts

SOAP (Simple Object Access Protocol)

Used with HTTP for web service access.

Part of web service architecture.

Used for retrieval of data in request and response.

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Basic Concepts

Web Service Architecture

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Basic Concepts

Web Engineering

Systematic system of steps for developing web

applications.

Contains the traditional steps of software

engineering from requirement engineering till

testing and deployment.

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Basic Concepts

Tools for Web Development

MS Front Page

Dreamweaver

.NET Framework

etc

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Q& A

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TASK # 1

Visit following web site;

www.geocities.com

Explore how you can upload a page from your computer

on Geocities Server.

Create a Page in MS Front Page [showing your name,

registration number, class and insert any picture on web

page] and upload it to Geocities Server.

Submit only URL of your web page on 16th Feb 09

[BSSEF06] and 17th Feb 09 [BSCS F06].