Introduction to the Internet & WWW by Dr. Khalil 1 Introduction to the Internet and World Wide Web Dr. Awad Khalil Computer Science Department AUC

Introduction to the Internet & WWW by Dr. Khalil

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Introduction to the Internet and

World Wide Web

Dr. Awad KhalilDr. Awad Khalil

Computer Science DepartmentComputer Science Department

AUCAUC


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Internet Protocols

Web Environment – the InternetWeb Environment – the Internet Internet HistoryInternet History Internet CharacteristicsInternet Characteristics The Web Building BlocksThe Web Building Blocks Intranet & ExtranetIntranet & Extranet Intranet ServicesIntranet Services HTTPHTTP Web ApplicationsWeb Applications


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Web Environment – The Internet The Internet is the new server for millions of clients. The Internet and The Internet is the new server for millions of clients. The Internet and

the World Wide Web are evolving rapidly, if not explosively.the World Wide Web are evolving rapidly, if not explosively.

The WWW now increases the prominence of the Internet in The WWW now increases the prominence of the Internet in information systems, strategic planning and implementation.information systems, strategic planning and implementation.

Organizations want to integrate the Internet Organizations want to integrate the Internet ““seamlesslyseamlessly”” into their into their information systems.information systems.

Internet technology is the most widely used and successful example Internet technology is the most widely used and successful example of client/server (thin client/fat server) technology in use today.of client/server (thin client/fat server) technology in use today.

The Internet has reached critical mass by allowing hundreds of The Internet has reached critical mass by allowing hundreds of millions of users to connect with each other, thus making it inevitable millions of users to connect with each other, thus making it inevitable that managers everywhere would see it as the new frontier to conquer that managers everywhere would see it as the new frontier to conquer in the quest for business profits and enhanced public services.in the quest for business profits and enhanced public services.

The use of Internet technologies facilitates the sharing of The use of Internet technologies facilitates the sharing of heterogeneous information in an environment that provides multiple heterogeneous information in an environment that provides multiple benefits at a fraction of the cost.benefits at a fraction of the cost.


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Web Environment – The Internet The Internet is the new server for millions of clients. The Internet and The Internet is the new server for millions of clients. The Internet and

the World Wide Web are evolving rapidly, if not explosively.the World Wide Web are evolving rapidly, if not explosively.

The WWW now increases the prominence of the Internet in The WWW now increases the prominence of the Internet in information systems, strategic planning and implementation.information systems, strategic planning and implementation.

Organizations want to integrate the Internet Organizations want to integrate the Internet ““seamlesslyseamlessly”” into their into their information systems.information systems.

Internet technology is the most widely used and successful example Internet technology is the most widely used and successful example of client/server (thin client/fat server) technology in use today.of client/server (thin client/fat server) technology in use today.

The Internet has reached critical mass by allowing hundreds of The Internet has reached critical mass by allowing hundreds of millions of users to connect with each other, thus making it inevitable millions of users to connect with each other, thus making it inevitable that managers everywhere would see it as the new frontier to conquer that managers everywhere would see it as the new frontier to conquer in the quest for business profits and enhanced public services.in the quest for business profits and enhanced public services.

The use of Internet technologies facilitates the sharing of The use of Internet technologies facilitates the sharing of heterogeneous information in an environment that provides multiple heterogeneous information in an environment that provides multiple benefits at a fraction of the cost.benefits at a fraction of the cost.


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History of the Internet

ARPAnetARPAnet Implemented in late 1960’s by ARPA (Advanced Implemented in late 1960’s by ARPA (Advanced

Research Projects Agency of DOD)Research Projects Agency of DOD) Networked computer systems of a dozen universities Networked computer systems of a dozen universities

and institutions with 56KB communications linesand institutions with 56KB communications lines Grandparent of today’s InternetGrandparent of today’s Internet Intended to allow computers to be sharedIntended to allow computers to be shared Became clear that key benefit was allowing fast Became clear that key benefit was allowing fast

communication between researchers – communication between researchers – electronic-mailelectronic-mail ((emailemail))


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History of the Internet (Cont’d)

ARPA’s goalsARPA’s goals Allow multiple users to send and receive info at same Allow multiple users to send and receive info at same

timetime Network operated Network operated packet switching packet switching techniquetechnique

Digital data sent in small packages called Digital data sent in small packages called packetspacketsPackets contained data, address info, error-control Packets contained data, address info, error-control

info and sequencing infoinfo and sequencing infoGreatly reduced transmission costs of dedicated Greatly reduced transmission costs of dedicated

communications linescommunications lines Network designed to be operated without centralized Network designed to be operated without centralized

controlcontrolIf portion of network fails, remaining portions still If portion of network fails, remaining portions still

able to route packetsable to route packets


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Transmission Control Protocol (TCP)Transmission Control Protocol (TCP) Name of protocols for communicating over Name of protocols for communicating over

ARPAnetARPAnet Ensured that messages were properly routed Ensured that messages were properly routed

and that they arrived intactand that they arrived intactOrganizations implemented own networksOrganizations implemented own networks

Used both for intra-organization and Used both for intra-organization and communication to route packetscommunication to route packets


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Huge variety of networking hardware and software Huge variety of networking hardware and software appearedappeared ARPA achieved inter-communication between all ARPA achieved inter-communication between all

platforms with development of the platforms with development of the IPIPInternetworking ProtocolInternetworking ProtocolCurrent architecture of InternetCurrent architecture of Internet

Combined set of protocols called TCP/IPCombined set of protocols called TCP/IP The InternetThe Internet

Limited to universities and research institutionsLimited to universities and research institutions Military became big userMilitary became big user Next, government decided to access Internet for Next, government decided to access Internet for

commercial purposescommercial purposes


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Internet traffic grewInternet traffic grew Businesses spent heavily to improve InternetBusinesses spent heavily to improve Internet

Better service their clientsBetter service their clients

Fierce competition among communications Fierce competition among communications carriers and hardware and software supplierscarriers and hardware and software suppliers

ResultResultBandwidthBandwidth (info carrying capacity) of (info carrying capacity) of

Internet increased tremendouslyInternet increased tremendouslyCosts plummetedCosts plummeted


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Internet traffic grewInternet traffic grew Businesses spent heavily to improve InternetBusinesses spent heavily to improve Internet

Better service their clientsBetter service their clients

Fierce competition among communications Fierce competition among communications carriers and hardware and software supplierscarriers and hardware and software suppliers

ResultResultBandwidthBandwidth (info carrying capacity) of (info carrying capacity) of

Internet increased tremendouslyInternet increased tremendouslyCosts plummetedCosts plummeted


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Internet Characteristics

Hardware and software independenceHardware and software independence Common and simple user interfaceCommon and simple user interface Location independenceLocation independence Rapid development at manageable costsRapid development at manageable costs


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The Web Building Blocks

InternetInternet World Wide Web (WWW World Wide Web (WWW

or Web)or Web) Web PageWeb Page HyperText Markup HyperText Markup

LanguageLanguage HyperlinkHyperlink Web browserWeb browser Static Web pageStatic Web page Dynamic Web pageDynamic Web page Web serverWeb server Web siteWeb site HyperText Transfer HyperText Transfer

ProtocolProtocol


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The Web Building Blocks (Cont’d)

1. Internet Worldwide network of Worldwide network of

computers connected computers connected together through a standard together through a standard network protocol known as network protocol known as Transmission Control Transmission Control Protocol/Internet Protocol, or Protocol/Internet Protocol, or TCP/IP, You can think of the TCP/IP, You can think of the Internet as the “highway” on Internet as the “highway” on which data travel, as in the which data travel, as in the phrase “the information phrase “the information super-highway.” The terms super-highway.” The terms Internet and World Wide Internet and World Wide Web are often used Web are often used interchangeably, but they are interchangeably, but they are not synonyms.not synonyms.

2. World Wide Web (WWW or Web)

Worldwide network of Worldwide network of servers that store servers that store collections of specially collections of specially formatted files known formatted files known as Web pages. The Web as Web pages. The Web is just one of many is just one of many services provided by the services provided by the Internet. However, it is Internet. However, it is the World Wide Web the World Wide Web that truly opened the that truly opened the Internet to the World.Internet to the World.


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3. Web Page A text document containing A text document containing

labels and special commands labels and special commands (or tags) written in a Markup (or tags) written in a Markup Language (HTML or XML).Language (HTML or XML).

4. HyperText Markup Language

Standard document-Standard document-formatting language for Web formatting language for Web pages.pages.

5. Hyperlink Web pages are linked to Web pages are linked to

each other – that is, each each other – that is, each Web page can call other Web page can call other Web pages – creating the Web pages – creating the effect of a “web.” Because effect of a “web.” Because this link can connect to this link can connect to different types of documents different types of documents such as text, graphics, such as text, graphics, animated graphics, video, animated graphics, video, and audio, it is known as a and audio, it is known as a “hyperlink.”“hyperlink.”


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6. Web browser The end user application The end user application

used to browse or navigate used to browse or navigate (jump from page to page) (jump from page to page) through the Web. The through the Web. The browser is a graphical browser is a graphical interface that runs on the interface that runs on the client computer, and its client computer, and its main function is to display main function is to display Web pages. The Web Web pages. The Web browser (e.g., Netscape browser (e.g., Netscape Navigator, Internet Navigator, Internet Explorer) requests Web Explorer) requests Web pages from the Web server.pages from the Web server.

7. Static Web page A Web page whose contents A Web page whose contents

remain the same (when viewed in a remain the same (when viewed in a browser) unless the page is browser) unless the page is manually edited. An example of a manually edited. An example of a static Web page is a standard price static Web page is a standard price list posted by a manufacturer.list posted by a manufacturer.

8. Dynamic Web page A Web page whose contents are A Web page whose contents are

automatically created and tailored automatically created and tailored to an end user’s needs each time to an end user’s needs each time the end user requests the page. For the end user requests the page. For example, an end user can access a example, an end user can access a Web page that displays the latest Web page that displays the latest stock selections entered by that end stock selections entered by that end user.user.


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9. Web server A specialized application whose A specialized application whose

only function is to “listen” for only function is to “listen” for clients’ requests and to send the clients’ requests and to send the requested Web page(s).requested Web page(s).

10. Web site Term used to refer to the Web Term used to refer to the Web

server and the collection of Web server and the collection of Web pages stored on the local hard disk pages stored on the local hard disk of the server computer or an of the server computer or an accessible shared directory. The accessible shared directory. The Web server and the Web client Web server and the Web client communicate using a special communicate using a special protocol known as HyperText protocol known as HyperText Transfer Protocol or HTTP.Transfer Protocol or HTTP.

11. HyperText Transfer Protocol

The standard protocol The standard protocol used by the Web used by the Web browser and Web browser and Web server to communicate. server to communicate.

XML, by Dr. Khalil 17

Evolution !!


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Intranet & Extranet

Intranet is a locally owned is a locally owned and operated Internet and operated Internet whose access is carefully whose access is carefully controlled. controlled.

Intranet architecture is Intranet architecture is based on the same basic based on the same basic components of the components of the Internet: Web servers, Internet: Web servers, clients using Web browser, clients using Web browser, the TCP/IP and HTTP the TCP/IP and HTTP protocols, and protocols, and HTML/XML formatting.HTML/XML formatting.

An An Extranet extends the extends the Intranet to the Intranet to the corporation’s value chain. corporation’s value chain.


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HTTP


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HTTP

HTTP is based on a HTTP is based on a request-response paradigm:request-response paradigm: ConnectionConnection – the – the

client establishes a client establishes a connection with the connection with the Web serverWeb server

RequestRequest – The client – The client sends a request sends a request message to the Web message to the Web server.server.

Response Response – The Web – The Web server sends a response server sends a response (e.g., an HTML (e.g., an HTML document) to the document) to the client.client.

Close Close – The – The connection is closed by connection is closed by the Web server.the Web server.


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HTTP Request An HTTP request consists o a header An HTTP request consists o a header

indicating the type of request, the indicating the type of request, the name of a resource, the HTTP version, name of a resource, the HTTP version, followed by optional body. The main followed by optional body. The main HTTP request types are:HTTP request types are: GETGET – Retrieves (gets) the – Retrieves (gets) the

resource the user has requested.resource the user has requested. POSTPOST – Transfers (posts) data to – Transfers (posts) data to

the specified resource.the specified resource. HEADHEAD – Returns only an HTTP – Returns only an HTTP

header instead of response data.header instead of response data. PUTPUT Uploads the resource to the Uploads the resource to the

server.server. DELETEDELETE – Deletes the resource – Deletes the resource

from the server.from the server. OPTIONSOPTIONS – Requests the server’s – Requests the server’s

configuration options.configuration options.


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HTTP

HTTP is currently a stateless protocol – the HTTP is currently a stateless protocol – the server retains no information between requests.server retains no information between requests.

This means that the information a user enters on This means that the information a user enters on one page is not automatically available on the one page is not automatically available on the next page requested.next page requested.

The stateless property of HTTP makes it difficult The stateless property of HTTP makes it difficult to support the concept of a session that is to support the concept of a session that is essential to basic DBMS transactions.essential to basic DBMS transactions.


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Web Application

Advantages SimplicitySimplicity Platform independencePlatform independence Graphical User InterfaceGraphical User Interface StandardizationStandardization Cross-platform supportCross-platform support Transparent network Transparent network

accessaccess Scalable deploymentScalable deployment InnovationInnovation

Disadavantages ReliabilityReliability SecuritySecurity CostCost ScalabilityScalability Limited functionality of Limited functionality of

HTMLHTML StatelessStateless BandwidthBandwidth PerformancePerformance Immaturity of development Immaturity of development

toolstools


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Web Application Architecture

Web applications may be created Web applications may be created using various approaches. using various approaches. However, there are a number of However, there are a number of components that will form components that will form essential building blocks for such essential building blocks for such applications. Typically, the Web applications. Typically, the Web application architecture is a three-application architecture is a three-tier architecture in which:tier architecture in which: A Web Browser acting A Web Browser acting

as the “thin” client.as the “thin” client.

A Web Server acting as A Web Server acting as the application server.the application server.

A Database Server acting A Database Server acting as the third tier.as the third tier.


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Browser Layer The browser is the client of a Web application, and it The browser is the client of a Web application, and it

has two major functions:has two major functions: First, it handles the layout and display of HTML First, it handles the layout and display of HTML

documents. documents.

Second, it executes the client-side extension Second, it executes the client-side extension functionality such as Java, JavaScript, and ActiveX functionality such as Java, JavaScript, and ActiveX (a method to extend a browser’s capabilities). (a method to extend a browser’s capabilities).

The two most popular browsers at the present are The two most popular browsers at the present are Netscape Navigator (Netscape for short) and Microsoft Netscape Navigator (Netscape for short) and Microsoft Internet Explorer (IE). They have their own advantages Internet Explorer (IE). They have their own advantages and disadvantages with respect to Web applications.and disadvantages with respect to Web applications.


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IE versus Netscape Both browsers support Java, JavaScript, and IE also Both browsers support Java, JavaScript, and IE also

supports ActiveX.supports ActiveX.

Netscape is supported on numerous platforms, whereas Netscape is supported on numerous platforms, whereas IE runs only on Microsoft systems (e.g., Windows 2000, IE runs only on Microsoft systems (e.g., Windows 2000, 98 and NT).98 and NT).

IE offers compatibility with other Microsoft products and IE offers compatibility with other Microsoft products and can easily be integrated with existing tools such as Word, can easily be integrated with existing tools such as Word, Excel and PowerPoint. The drawback is that IE heavily Excel and PowerPoint. The drawback is that IE heavily dependent on the Windows platforms and other dependent on the Windows platforms and other Microsoft proprietary systems. Microsoft proprietary systems.

ActiveX is designed to extend the functionality of IE, and ActiveX is designed to extend the functionality of IE, and works only on Windows platforms and Macintosh works only on Windows platforms and Macintosh System 7+.System 7+.


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The Application Logic Layer The application logic layer is the part of a Web The application logic layer is the part of a Web

application with which a developer will spend the application with which a developer will spend the most time. It is responsible for:most time. It is responsible for:

collecting data for a query (e.g., an SQL collecting data for a query (e.g., an SQL statement);statement);

preparing and sending the query to the preparing and sending the query to the database via the database connection layer;database via the database connection layer;

retrieving the results from the connection layer;retrieving the results from the connection layer;

formatting the data for display.formatting the data for display.


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The Application Logic Layer (Cont’d)


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The Database Layer

This is the place where the underlying database resides This is the place where the underlying database resides within the Web database application.within the Web database application.

The database is responsible for storing, retrieving, and The database is responsible for storing, retrieving, and updating data based on user requirements, and the updating data based on user requirements, and the DBMS can provide efficiency and security measures.DBMS can provide efficiency and security measures.

In many cases, when developing a Web application, the In many cases, when developing a Web application, the underlying database has already been in existence. A underlying database has already been in existence. A major task, therefore, is to link the database to the Web major task, therefore, is to link the database to the Web (the connection layer) and to develop the application (the connection layer) and to develop the application logic layer.logic layer.


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The Database Connection Layer

This is the component which actually links a database to the Web server.This is the component which actually links a database to the Web server.

Many current Web database building tools offer database connectivity solutions Many current Web database building tools offer database connectivity solutions and they are used to simplify the connection process.and they are used to simplify the connection process.

The database connection layer provides a link between the application logic layer The database connection layer provides a link between the application logic layer and the DBMS. Connection solutions come in many forms, such asand the DBMS. Connection solutions come in many forms, such as DBMS net protocols, DBMS net protocols, API (Application Programming Interface) or class libraries, and programs that API (Application Programming Interface) or class libraries, and programs that

are themselves database clients. Some of these solutions resulted in tools being are themselves database clients. Some of these solutions resulted in tools being specifically designed for developing Web database applications.specifically designed for developing Web database applications.

In Oracle, for example, there are native API libraries for connection and a number In Oracle, for example, there are native API libraries for connection and a number of tools, such as Web Publishing Assistant, for developing Oracle applications on of tools, such as Web Publishing Assistant, for developing Oracle applications on the Web. the Web.

The connection layer within a Web database application must accomplish a number of The connection layer within a Web database application must accomplish a number of goals. They have to provide access to the underlying database, and they also need to be easy goals. They have to provide access to the underlying database, and they also need to be easy to use, efficient, flexible, robust, reliable, and secure. Different tools and methods fulfill to use, efficient, flexible, robust, reliable, and secure. Different tools and methods fulfill these goals to different extents.these goals to different extents.


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The Database Connection Layer (Cont’d)


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Thank you

Documents

Introduction to the Internet & WWW by Dr. Khalil 1 Introduction to the Internet and World Wide Web Dr. Awad Khalil Computer Science Department AUC