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SE 341 Web Application Development
Lecture 2
SPRING 2009
Muneera BanoAssistant Professor DCS, FBAS, IIU
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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].