web engineering notes unit 2

ST.ALOYSIUS INSTITUTE OF TECHNOLOGY,JABALPUR Web Engineering (CS-802) Unit-1

Introduction to Web Engineering

Web Engineering, an emerging new discipline, advocates a process and a systematic approach to development of high quality Web-based systems. It promotes the establishment and use of sound scientific, engineering and management principles, and disciplined and systematic approaches to development, deployment and maintenance of Web-based systems.

It incorporates some of the well-known and successful traditional and software „engineering‟ principles and practices, adopting them to more open and flexible nature of the Web, and the type of Web application. It also takes into consideration other elements that are specific to the Web environment.

In particular, web engineering focuses on the methodologies, techniques and tools that are the foundation of web application development and which support their design, development, evolution, and evaluation. Web application development has certain characteristics that make it different from traditional software, information system, or computer application development.

Web engineering is multidisciplinary and encompasses contributions from diverse areas: systems analysis and design, software engineering, hypermedia/hypertext engineering, requirements engineering, human-computer interaction, user interface, information engineering, information indexing and retrieval, testing, modeling and simulation, project management, and graphic design and presentation (as shown in below figure)

Web engineering is neither a clone, nor a subset of software engineering, although both involve programming and software development. While web Engineering uses software engineering principles, it encompasses new approaches, methodologies, tools, techniques, and guidelines to meet the unique requirements of web-based applications.

Prepared By : Mr.Aditya Patel


History of Web Development

What is Web Development? Web development is a broad term for the work involved in developing a web site for the Internet (World Wide Web) or an intranet (a private network). This can include web design, web content development, client liaison, client-side/server-side scripting, web server and network security configuration, and e-commerce development. However, among web professionals, "web development" usually refers to the main non-design aspects of building web sites: writing markup and coding. Web development can range from developing the simplest static single page of plain text to the most complex web-based internet applications, electronic businesses, or social network services.

Web Development history can be explained in following points:

The world of web development has come a long way! Once upon a time, developers would create HTML (Hypertext Markup Language) pages by typing in code for each page that was to be part of a web site. For example, <b>hello world</b> would result in "hello world".

HTML editors such as Dreamweaver came on the scene and creating code became much easier: a developer could highlight "hello world," click on the bold icon in the editor, and get "hello world" While this saved time, web code editing software were stand-alone purchases that cost hundreds of dollars and had to be installed on high performance computers.

In order to appreciate the evolution of web development, one must understand the difference between static and dynamic HTML. In a static world, developers would create HTML pages one-by-one. Each static HTML page was independent from all others. In a dynamic world, developers could change a single file (php, asp, cfm and MANY others) that would then change other files. For example, a header file with navigation (home, contact, about us, etc) may needed to be updated often. Static HTML would be a slow way to update the entire web site when a new page is added.

So, a smart developer would create an index.php file (home page) that says, "when I get loaded, also load the file called header.php" This means that every subsequent page (such as about_us.php, contact_us.php) would also get updated automatically when header.php changes.

Along with the development of desktop software for web developers, a movement to create web sites without having to download any desktop software had begun. The theory was that users could use an Internet browser such as Netscape, Firefox, Safari and / or Internet Explorer to login and then make changes to their web site. The solutions were built using dynamic pages as described above, and also connected to a database. These solutions were called Content Management Systems (CMS).



Web Development Timeline:

In June 1993, Matthew Gray at MIT ran a small program which automatically travels links within the Web network to try to determine just how many sites there are that offer information over the World Wide Web.

His small ―World Wide Web Wanderer‖ found around 100 sites that month and over two

hundred thousand documents. In March 1994 his robot found over 1200 unique sites. Even

though the robot‟s programming was improved somewhat, and a number of factors may have

affected the final count, the growth rate of the web form the last half of 1993 throughout the first

half of 1994 is amazing and continues to increase.

Motivation of Web Development:

Developers of analytical applications often struggle with the need to present complicated information in a way users can best understand it. Often the developers will rely on insightful visualization techniques and good user interface design. These approaches are not trivial, and for some applications cannot convey information simply enough for all users, especially students, novices and those unfamiliar with the low-level details of the application domain (such as a non technical manager who must make decisions based on a developer‟s work). Even for applications with straightforward information displays, users may still have questions about what a particular item means or how it was determined.



To complicate the developer‟s job, users often have different mental models of an application than the developer. Even when developers work closely with users, the end result might not be equally intuitive for all users or serve each user‟s individual tasks equally well. A user may wish to access a particular display, function or piece of information which he or she believes is immediately relevant to the task at hand, but which the system does not make accessible from the current screen or immediate vicinity.

Categories of Web Applications:

1) Document Centric (Static homepage, web radio, company web site)

Document centric Websites are the precursor to Web applications. Web pages are stored on a Web Server as ready-made, i.e. static, HTML documents and sent to the web client in response to request. These web pages are usually manually using respective tools. Especially for web sites requiring frequent changes or for sites with huge number of pages this is a significant cost factor and often results in outdated information. Additionally, there a danger of inconsistencies, as some content is frequently represented redundantly on several web pages for easy access. The benefits are the simplicity and stability of such web sites and the short response time, as the pages are already stored on the web server. Static homepages, webcasts, and simple web presences for small business belong in this category.

2) Interactive ( Virtual exhibition, news site, travel planning )

With the introduction of the Common Gateway Interface and HTML forms, interactive web applications emerged, offering a first, simple, form of interactivity by means of forms, radio buttons and selection menus. Web pages and links to other pages are generated dynamically according to user input. Examples of this category are virtual exhibitions, news sites, or timetable information.

3) Transactional ( online banking, shopping, booking system )

Transactional web applications were created to provide more interactivity, giving the user the possibility of not only interacting with the application in a read-only manner, but also by performing updates on the underlying content. Considering a tourism information system this would allow, for example, updating the content in a decentralized way or making it possible to book rooms.

4) Workflow based ( E government, B2B solution, Web-based support )

It allows the handling of workflows within or between different companies, public authorities, and private users. A driving force for this is the availability of appropriate web services to guarantee interoperability. The complexity of the services in question, the autonomy of the participating companies and the necessity for the workflows to be robust and flexible are the main challenges.

5) Collaborative ( chat room, E learning platform, P2P-services )



Collaborative web applications are employed especially for cooperation purposes in unstructured operations. There is need for communication between the cooperating users is particularly high. Collaborative web applications support shared information and workspaces in order to generate, edit, and manage shared information.

6) Portal oriented ( community portal, online shopping mall, business portal )

Portal-oriented web applications provide a single point of access to separate, potentially heterogeneous sources of information and services, makers of browsers, such as Microsoft and Netscape, search engines such as Yahoo, online services such AOL, media conglomerates, and other companies have become aware of the demand for this and now offer central hubs, so called portals, as a point of access to the web.

7) Ubiquitous (customized services, location aware services, Multi platform delivery )

A ubiquitous web application is a Web application that suffers from the anytime/anywhere/any media syndrome. This means that an ubiquitous web application should be designed from the start taking into account not only its hypermedia nature, but also the fact that it must run ―as is‖ on a variety of platforms, including mobile phones, Personal Digital Assistants (PDAs), full-fledged desktop computers, and so on. This implies that an ubiquitous web application must take into account the different capabilities of devices comprising display size, local storage size, method of input, network capacity, etc

8) Semantic ( Knowledge management, syndication, recommender system )

The Semantic Web is a collaborative movement led by the World Wide Web Consortium (W3C) that promotes common formats for data on the World Wide Web. By encouraging the inclusion of semantic content in web pages, the Semantic Web aims at converting the current web of unstructured documents into a "web of data". It builds on the W3C's Resource Description Framework (RDF).

9) Social (web logs, collaborative filtering, Virtual shared workplace )

The social Web is a set of social relations that link people through the World Wide Web. The Social

web encompasses how websites and software are designed and developed in order to support and foster social interaction. These online social interactions form the basis of much online activity including online shopping education, gaming and social networking websites.These tastes vary depending on who the target audience is, and what they are looking for. For individuals working in the public relation department, the job is consistently changing and the impact is coming from the social web. The influence, held by the social network is large and ever changing.



Characteristics of Web Applications:

The characteristics reviewed will be grouped into these four factors.

1) Users:

The stakeholders of a web application can be categorized by the users affected by the web interface: primary users, secondary users, user communities, users as buyers, and surrogate users.

Primary users of a web application can be examined based on their competence, which will

change over time: novice, advance beginners, competent performers, and experts. This

competence can be examined from three perspectives: subject matter knowledge, computer

skill, and experience with the web application.

The loyalty of users to a web application is an important characteristic, especially to e-

commerce web applications. The basic spectrum of loyalty to a web application is

discretionary or compulsory. For example, a particular book can be purchased on Amazon or

Barnes and Noble or a local bookstore such as Dymocks. The user has discretion to decide

which alternative to use to make the purchase, whereas an organization‘s intranet gives users

no alternative (compulsory) web application. Users can perform transactions on a web

application with varying levels of credentials. Accessibility is an important characteristic of

a web application. Accessibility focuses on people with disabilities. A web application needs



to consider assistive technologies, and compliance to the Web Content Accessibility. This

characteristic can impact on many of the other characteristics of a web application, like the

impact of interaction styles and support for different input and display devices (system

variables). For example, a visually impaired user may use a screen magnifier or Braille

display device, which requires support for alternative devices.

Motivational factors, as discussed by Zhang et al. (1999), can include: Work Itself being

challenging, stimulating, interesting, meaningful, useful, creative and fun; Achievement with

successful completion of task(s); Responsibility given through user control; Advancement

and Growth through the gain in knowledge and skills.

2) Task:

Deshpande et al. (2002) proposed the following taxonomy of web applications categories:

informational, interactive, transaction, workflow, collaborative work environments, online

communities (market places), web portals, web services. Transactional type web applications

are commonly found in e-commerce applications and can be further broken down into:

transaction type, domain/site type, vendor type and product type. The interaction style that

can be implemented on a web application is constrained by the technological aspects. The

interaction styles provide various levels of usability, and support different types of users,

these could include: Batch, Question-answer, Command language, Function keys, Form fill-

in, Menus, Direct manipulation, Non-command, Natural language. The interface design

characteristic of a web application can be represented by its: structure describes the

organization of the information space presented by a web application; navigation enables

moving through the information space presented by the web application; presentation

describes the interaction styles used to present the information and behavior of the web

application.

3) Technology:

The tools used to implement a web application can dictate the degree of usability possible,

through the architecture developed with the tool. Fraternali (1999) describes these various

web development tools as: visual editors and site managers; hypermedia web generators;

web database gateways; web-based form editors and database web publishing wizards;

model-driven application generators. Microsoft PowerPoint allows publishing of its

presentations using and export into HTML, with a publishing wizard. This tool limits the

implementation of characteristics, such as design, interaction style, and aesthetics.

Development of web application can be for intranet, or internet networks. Karlsbjerg (2003)

describes implementation strategies for intranet web applications from two perspectives.

First, the architecture of the web application is tailor-made or ready-made. Second, it is



implemented or configured in-house or outsourced. This ownership characteristic of the web

application, impacts on the ease by which the web application can dynamically meet the

needs of the website owner and its visitors in web time.

4) Context:

An industry classification provides the context of the environment where the users perform

the interaction. An industry classification is a characteristic of a web application that

highlights special needs of an industry in relation to usability. For example, finance industry

requires greater focus on security, while government web applications need greater focus on

accessibility. There is a major industry classification prescribed by the Australian Bureau of

Statistics, that includes: Agriculture, Forestry and Fishing; Mining; Manufacturing;

Electricity, Gas and Water Supply; Construction; Wholesale Trade; Retail Trade;

Accommodation, Cafes and Restaurants; Transport and Storage; Communication Services;

Finance and Insurance; Property and Business Services; Government Administration and

Defence; Education; Health and Community Services; Cultural and Recreational Services;

Personal and Other Services.

The contextual properties of a user that is interacting with a web application can vary with

each web application. User context allows identification and enables personalization.

Network provides network and bandwidth context. Location captures information about the

location that can enhance context of web application. Time context represented at a web

server may dictate opening and closing times or relate to a timetable or schedule.

Evolution & Need for Web Engineering:

Evolution:

The need for evolution can be argued for wth the continuous change of requirements and conditions, the competitive pressure, and the general fast pace of development:

Continuous change: Web applications change rapidly and are therefore subject to

permanent evolution due to constantly changing requirement or conditions. The rapid and

never ending change of web technologies and standards in particular makes it necessary

to continuously adapt web applications to these. This has two reasons- users want the

newest web type, and the used tools are also technology driven. This constant change of

requirements and conditions is a central characteristic of web applications. Changes may

concern all three dimensions of a web application – the product itself, its usage, and in

particular, its development.

Competitive pressure: The extremely high competitive pressure on the Web, the time to market pressure and the necessity for a web presence, increase the need for ever shorter



product lifecycles and extremely short development cycles and apparently leave no room

for systematic development process. Immediate web presence is considered more

important than long term perspective.

Fast pace: The extreme time pressure on web application development is due to the rapid

change on the web and the accordingly short lifespans of web applications or their

frequency of updates. While for conventional software, evolution takes place in a planned

series of versions, it is continuous for web applications. This means that web applications

are in permanent maintenance. The cycle of change is often no longer than a few days or

weeks. Web applications therefore require ―lean‖ versions of traditional software

engineering processes with special emphasis on requirement analysis and specification on

the one hand and operation and maintenance on the other.

Needs:

Need for web engineering has been stressed, where scientific principles are the result of applying

a scientific process. A process in this context means that our current understanding, i.e. our

theory of how best to develop, deploy and maintain high quality web based systems and

applications, may be modified or replaced as new evidence is found through the accumulation of

data and knowledge. This process is illustrated and described below:

Observation: To observe or read about a phenomenon or set of facts. In most cases the

motivation for such observation is to identify cause and affect relationships between

observed items, since these entail predictable results. For example, we can observe that

an increase in the development of new web pages seems also to increase the

corresponding development effort.

Hypothesis: To formulate a hypothesis represents an attempt to explain an observation. It

is a tentative theory or assumption that is believed to explain the behavior under

investigation. The items that participate in the observation are represented by variables

(eg number of new web pages, development effort) and the hypothesis indicates what is

expected to happen to these variables (eg there is a linear relationship between number of

new web pages increases so does the effort to develop these pages.) These variables first

need to be measured and to do so we need an underlying measurement theory.

Prediction: To predict means to predict results that should be found if the rationale used

in the hypothesis formulation is correct (eg web applications with larger number of new web pages will use a larger development effort).

Validation: To validate requires experimentation to provide evidence either to support or refute the initial hypothesis. If the evidence refutes the hypothesis then the hypothesis



should be revised or replaced. If the evidence is in support of the hypothesis, then many

more replications of the experiment need to be carried out in order to build a better

understanding of how variables relate to each other and their cause and effect

relationships.

Web Engineering Models:

1) Levels – Information, node/link structure, UI & page layout separate. 2) Aspects – Same as Software Applications 3) Phases – Approach depends upon type of application 4) Customization – Context information

Software Engineering v/s Web Engineering:

Though Web engineering involves some programming and software development, and adopts some of the principles of the software engineering, Web-based system development is different from software development, and also Web engineering is different from software engineering.

1) Most Web-based systems, at least as of now, are document-oriented containing static or dynamic Web pages.

2) Web-based systems will continue to be focused on look and feel, favoring visual creativity

and incorporation of multimedia (in varying degrees) in presentation and interface. More emphasis will be placed on visual creativity and presentation as regards to the front-end interface with which a user interacts.



3) Most Web-based systems will continue to be content-driven – often Web-based systems development include development of the content presented.

4) Multiplicity of user profiles – Most Web-based systems need to cater to users with diverse

skills and capability, complicating human-computer interaction, user interface and information presentation.

5) The nature and characteristics of the medium of Web is not well understood as the software

medium.

6) The Web exemplifies a greater bond between art and science than generally encountered in

software development.

7) Most Web-based systems need to be developed within a short time, making it difficult to

apply the same level of formal planning and testing as used in software development.

10) Also Web is different from software as related to the delivery medium.

11) Further, the type of individuals who build/develop Web-based systems are vastly varied in

their background, skills, knowledge and system understanding, and as well as their perception of Web and quality Web-based system.



Introduction to TCP/IP:

Since TCP/IP is fundamental to the definition of the Internet, it‘s natural to begin our study of

Internet protocols with these protocols. Yes, I said protocols (plural), because although so far I

have treated TCP/IP as if it were a single protocol, TCP and IP are actually two different

protocols. The reason that they are often treated as one is that the bulk of the services we

associate with the Internet—e-mail, Web browsing, file downloads, accessing remote

databases—are built on top of both the TCP and IP protocols. But in reality, only one of these

protocols—IP, the Internet Protocol—is fundamental to the definition of the Internet.

TCP/IP grew with the Internet and because LANs also became popular soon, connecting LANs

was one of the early goals of TCP/IP. In fact, when multiple networks with multiple

frame/datagram formats and also multiple other algorithms (routing, error control, compression

etc.) are to be connected, there are two alternatives which are a) Protocol conversion, b) A

universal protocol with its frame/datagram size and other algorithms operating at every node in

every network in addition to the existing protocols with algorithms of converting to/from that

network‘s frame/datagram from/to the frame/datagram of the universal protocol.

Generally the TCP/IP model is used in modern computers. It has five layers as shown in figure.

Network Access Layer:

This layer deals with the hardware level, voltages, etc. This layer ensures the safe and efficient transmission of data. It consists of electronic circuits for transmission of data.

This covers the Media Access and Control (MAC) strategies – i.e., who can send data and when, etc. This also deals with the frame formats.

Internet Layer:

This layer is concerned with the format of datagram, as defined in the Internet Protocol



(IP), and also about the mechanism of forwarding datagram‘s from the source computer

to the final destination via one or more routers. Thus, this layer is also responsible for

actual routing of datagram‘s. This layer makes internetworking possible, and thus creates

an illusion of a virtual network. The IP portion of the TCP/IP suite deals with this layer.

It routes and forwards a datagram to the next hop, but is not responsible for the accurate

and timely delivery of all the datagram‘s to the destination in a proper sequence. Other

protocols in this layer are ARP, RARP, ICMP.

Transport Layer:

Two main protocols are used in this layer and those are TCP and UDP. The transport

layer ensures that packets are received in the order they were sent. It also finds that no

data is lost or corrupted. In case, if a packet is lost, the transport layer can ask the sender

to retransmit the packet. The network implements this by adding an additional header to

each datagram that contains more information. The TCP protocol performs the task of

retransmission of lost or corrupted data. It is also responsible for transmission of data in

correct sequence. The UDP allows the receiver to detect corrupted packets but does not

guarantee that packets are delivered in the correct order.

Application Layer:

This layer allows an end user to run various applications on the Internet and use the Internet in different ways. These applications are FTP, TFTP, SMTP,TELNET and HTTP.

Introduction to WAP:

The Wireless Application Protocol (WAP) is a new advanced intelligent messaging service for

digital mobile phones and other mobile terminals that will allow you to see Internet content in

special text format on special WAP-enabled mobile phones. Enabling information access from

handheld devices requires a deep understanding of both technical and market issues that are

unique to the wireless environment. The WAP specification was developed by the industry‘s best

minds to address these issues. Wireless devices represent the ultimate constrained computing

device with limited CPU, memory and battery life and a simple user interface. Wireless networks

are constrained by low bandwidth, high latency and unpredictable availability and stability. The

WAP specification addresses these issues by using the best of existing standards and developing

new extensions when needed. The WAP solution leverages the tremendous investment in web

servers, web development tools, web programmers and web applications while solving the

unique problems associated with the wireless domain. The specification ensures that this solution

is fast, reliable and secure. The WAP specification is developed and supported by the wireless

telecommunication community so that the entire industry and its subscribers can benefit from a

single, open specification.



Why WAP is necessary?

The need of WAP can be explained by following points.

1) Ensure interoperability:

Service providers must feel secure that their investments will yield benefits in the future.

They will not be able to do so until equipment and software offered by different suppliers

can be made to work together. The WAP specification has been designed to encourage easy,

open interoperability between its key components. Any solution component built to be

compliant with the WAP specification can interoperate with any other WAP-compliant

component. Service providers can choose equipment and software from multiple WAP-

compliant vendors, selecting each piece of the solution that is appropriate for the service

provider‘s particular needs.

Bearer and device independence both help foster interoperability. But interoperability goes

beyond these two principles to require that each WAP-compatible component will

communicate with all other components in the solution network by using the standard

methods and protocols defined in the specification.

2) Encourage and Foster Market Development:

The WAP specification is designed to bring Internet access to the wireless mass market. By

building open specifications, and encouraging communication and technical exchanges

among the industry players, the WAP Forum has already begun to open the wireless data

market in new ways. Just over a year ago, the idea of a single wireless data standard was

unheard of, yet today the WAP specification is available to the public, and dozens of

companies are promoting this vision of the future. The revolution is under way to bring



information access to any handset, at a reasonable price and in an easy to use form factor.

3) The Market Is Different:

Bringing computing power to a wireless handset opens an extensive new market for

information access. This market is very different from the traditional desktop or even the

laptop market because the subscriber has a different set of needs and expectations. Some of these differences include:

a. Ease of use b. Market size c. Price sensitivity d. Usage patterns e. Essential tasks

4) The Network Is Different:

Wireless data networks present a more constrained communication environment compared to wired networks. Because of fundamental limitations of power, available spectrum and mobility, wireless data networks tend to have:

a. Less bandwidth:

WAP addresses this issue by minimizing the traffic over the interface. WML and WMLScript are binary encoded into a compact form when sent over the air in order to minimize the number of bits and bytes.

• High latency

Wireless networks have high latency compared to wired networks. This is addressed in WAP by minimizing the roundtrips between the wireless device and the wireless network.

• Less predictable availability

Wired network access provides a more or less reliable connection to the network. That is not

the case in wireless networks where bearers might be inaccessible for shorter or longer

periods of time due to fading, lost radio coverage or deficient capacity. The problem

mentioned above is addressed by allowing lost sessions to be resumed. Selective

retransmission is also employed to retrieve small segment of a message that are lost.

Furthermore, as bandwidth increases, the handset‘s power consumption also increases which further taxes the already limited battery life of a mobile device. A wireless data

solution must be able to overcome these network limitations and still deliver a satisfactory

user experience.



5) The Device Is Different:

Handheld wireless devices present a more constrained computing environment compared to desktop computers. Because of fundamental limitations of battery life and form factor, mass-market handheld devices tend to have:

• Less powerful CPUs • Less memory (ROM and RAM) • Restricted power consumption • Smaller displays • Different input devices (e.g., a phone keypad, voice input, etc.)

Because of these limitations, the user interface of a wireless handset is fundamentally different than that of a desktop computer. The limited screen size and lack of a mouse requires a different user interface metaphor than the traditional desktop GUI.

Introduction to DNS:

A domain name is a name given to a network for ease of reference by humans. The term domain actually refers to a group of computers that are called by a single common name.

In the early days of the Internet, all domain names and their associated IP addresses were recorded in a single file called host.txt. The Network Information Center in the US maintained this file.



The Domain Name System (DNS) was developed as a distributed database. By distributed, we mean that the database containing the mapping between the domain names and IP addresses was scattered across different computers. This DNS is consulted whenever any message is to be sent to any computer on the Internet.

Following table shows general domain names:

Domain name Description Com Commercial organization Edu Educational institution Gov Government institution Int International organization Mil Military group Net Network support group Org Non-profit organization

The DNS is based on the creation of a hierarchical domain-based naming architecture, which is implemented as distributed database, as remarked earlier. In simple terms, it is used for mapping host names and email addresses to IP addresses.



Following table shows proposed general domain names:

Domain name Description Arts Cultural organization Firm Business unit or firm Info Information service provider Nom Personal nomenclature Rec Recreation or Entertainment group Store Business offering goods/service Web Web-related organization

Introduction to Email:

Electronic main (email) was created to allow two individuals to communicate using computers. Email facility allows many features, given below-

Composing and sending/receiving a message.

Storing/forwarding/deleting/replying to a message with normally expected facilities, such as carbon copy (CC), blind carbon copy (BCC), etc.

Sending a single message to more than one person Sending text, voice, graphics and video. Sending a message that interacts with other computer programs.



The best features of email are given as follows: The speed of email is almost equal to that of telephonic conversation. The recording of the email messages in some form is like the postal system.

From the view point of users, email performs the following five functions.

1) Composition:

The email system can provide features in addition to the basic text editor features, such as automatic insertion of the receiver‘s email address when replying to a message.

2) Transfer:

The email system takes upon itself the responsibility of moving the message from the sender to the receiver, by establishing connections between the two computers and transferring the message using TCP/IP.

3) Reporting:

The sender needs to know whether the email message was successfully delivered to the receiver, or it did not reach the receiver for whatever reason. The email system performs this reporting task as well.

4) Displaying:

The email system displays the incoming messages in a special pop-up window, or informs the user in some way that an email message has arrived. The user can then open that message on the screen.

5) Disposition:

This includes features such as forwarding, archiving and deleting messages that have been dealt with. The user can decide what to do with such an email message, and instruct the email system accordingly.

Introduction to Telnet:

The Telnet protocol allows remote login services, so that user on a client computer can connect to a server on a remote system. Telnet has two parts, a client and a server. The client portion of Telnet software resides on a n end user‘s machine, and server portion resides on a remote server machine. That is, the remote server is the Telnet server, which provides an interactive terminal session to execute commands on the remote host. Once a user using the services of a Telnet client connects to the remote Telnet server computer, the keystrokes typed by the user on the client are sent to the remote server to be interpreted/acted upon to give an impression as if the user is using the server computer directly.

The interaction between a user and the server computer happens through a dumb terminal. Such a dumb terminal also has to have a microprocessor inside. Thus it can be considered to be a very primitive computer that simply has a keyboard, mouse and a screen and almost no processing power. In such an environment, all the processing is essentially done by the central server computer. When a user enters a command using the keyboard, for example, the command travels all the way to the server computer, which executes it and sends the results back to the user‘s terminal. At the same time, another user might have entered another command. This command



also travels to the server which processes it and sends the results back to that user‘s terminal. Neither user is concerned with the fact that the server is processing the requests from another user as well. Both users feel that they have exclusive access to the server resources.

Local login: In timesharing systems, all users log into the central server computer and use its resources. This is called as local login. A user‘s terminal sends the commands entered by the user to a program called as terminal driver, which is running on the central server computer. It is a part of the server computer‘s operating system. The terminal driver program passes the commands entered by the user to the appropriate module of the server computer‘s operating system. The operating system then processes these commands and invokes the appropriate application program, which executes on the server computer and its results are sent back to the user‘s terminal. This is shown in figure.

Remote login: In contrast to local login sometimes a user wants to access an application program located on a remote computer. For this, the user logs on to the remote computer in a process called as remote login. A user specifies the domain name or IP address to select a remote server with which it wants to establish a TELNET session. TELNET stands for TERminal NETwork.

Introduction to HTTP:

Hyper Text Transfer Protocol (HTTP) takes part in web browser and web server communication. Hence it is called a communication protocol. The basic feature of HTTP protocol is that it follows the request response model. The client makes a request for desired web page by giving the URL in the address bar. This request is submitted to the web server and then web server gives the response to the web browser by returning the required web page.

HTTP Request Message Structure:

The basic structure of request message is given by following general form-

Start line:

The start line consists of three parts which are separated by a single space. These parts are Request method

The method defines the CONNECT method which is used during the web browser and server communication. It is always written in Upper Case letters. The primary method in HTTP is GET. The GET method is used when- o You type a URL is address bar.



o When you click on some hyperlink which is present in the document. o When browser downloads images for display within a HTML document.

There is another commonly used method and i.e. POST. The POST method is typically used to send an information collected form a user form. Various methods used by HTTP are as given below-

HTTP Method Description

A browser used this command for requesting a web server for sending a particular GET web

page. This method is used to request the server for desired web page and the request

POST made is accepted as a new subordinate of the resource identified. The POST command is used to update an existing file with additional data This command does not request for a web page, but only requests for its header.

HEAD For instance, if a browser wants to know the last modified date of a web page, it would use the HEAD command rather than the GET command. This method supports for the specified URL. It can be used to check the

OPTION functionality of a web server by requesting ‗*‘ instead of a specific resource.

PUT PUT command sends a file to the server for storing it there. This command allows a browser to send an HTTP request for deleting a particular

DELETE web page.

TRACE When request is made using TRACE method the server echoes back the received request so that a client can see what intermediate servers are adding or changing in the request.

Request URI

The Uniform Resource Identifier (URI) is a string used to identify the names or resources on the Internet. The URI is a combination of URL and URN. The URL stands for Uniform Resource Locator and URN stands for Uniform Resource Name. The web address denotes the URL and specific name of the place or a person or item denotes the URN. For example-

Urn:ISBN 978-81-8431-123-2 specifies the address of some book.

Every URI consists of two parts, the part before the colon : denotes the scheme and the part after colon depends upon the scheme. The URIs are case insensitive but generally written in lower case. If the URI is written in the form of http:then it is both an URI and URL but there are some other URI which can also be used as URL. For example-

URL Intended Server

ftp://ftp.mywebsite.com/index.txt File can be located on FTP server



telnet://mywebsite.org

Telnet server

mailto:[email protected] Mail box

http://www.mywebsite.com Web server

HTTP Response Message Structure:

The structure of response message is similar to the request message structure. It is as follows-

1) Status line: Status line is similar to the start line in the request message. It consists of three fields-

HTTP version Status code Reason phrase

The HTTP version denotes the HTTP version such as HTTP/1.1. The status code is a numeric code indicating the type of response. The reason phrase is in the text string form and presents the information about the status code. For example:

2) Header fields: The header field in response message is similar to that of request message.

3) Blank line:

It is simply a blank line.

4) Message Body: The message body consists of response message.

Benefits of HTTP Protocol:

1) It is a communication protocol used between web browser and web server.‘

2) This protocol is based on request-response messaging. That means client makes the request of desired web page and then the server responds it by sending the requested resource.

3) It is a stateless protocol. That means HTTP protocol cannot remember the previous user‘s

information nor it remember the number of times the user has visited particular website. 4) The request-response message consists of plain text in fairly readable form.

5) The HTTP protocol has a cache control. This is an advanced feature of HTTP. Most of

the web browser automatically stores the recently visited web pages. This is very useful feature because if the user requests the same web page that has been visited already then it can be displayed form the cache memory instead of requesting the web server and bringing it from there.



Introduction to FTP:

When browsing the Web, downloading is initiated by clicking a hyperlink that references a document at an FTP (file transfer protocol) site. FTP is an older, but still popular, protocol for transferring information, especially large files, over the Internet.

An FTP site‘s URL begins with ftp://, rather than http://. FTP sites are typically accessed via hyperlinks (See Fig.), but can also be accessed by any software that supports FTP. Such software may or may not use a Web browser.

When the browser is pointed to an FTP site‘s URL, the contents of the specified site directory appear on the right side of the screen, with FTP information on the left. Two types of icons appear in the directory: files and directories. Files are downloaded by right clicking their icons, selecting Copy to Folder... and specifying the locations where the files are to be saved.

When a user visits an FTP site, IE5.5 sends the user‘s e-mail address and name (which is set by default to anonymous) to the site. This procedure occurs on FTP sites with public access, where any user is permitted access. Many FTP sites on the Internet have restricted access; only users with authorized user names and passwords are permitted to access such sites. When a user is trying to enter a restricted-access FTP site, a dialog like the one in Fig. is displayed, prompting the user for login information.

Transferring a file from the local machine to another location on the Internet is called uploading and can be accomplished using the FTP protocol. To place information on a Web site, the files must be uploaded to a specific restricted-access FTP server (this is dependent on the ISP). The



process involves uploading the file to a directory on the FTP site that is accessible through the Web. Web Browser:

Web browser is a kind of software which is basically used to use resources on the web.

Over the networks, two computers communicate with each other. In this communication, when request is made by one computer then that computer is called a client and when the request gets served by another computer then that computer is called server. Thus exchange of information takes place via Client-Server communication.

When user wants some web document then he makes the request for it using the web browser. The browsers are the programs that are running on the clients‘ machines. The request then gets served by the server and the requested page is then returned to the client. It is getting displayed to the client on the web browser.

Various web browsers that are commonly used are- Internet Explorer, Mozilla Firefox, Netscape Navigator and some other web browsers are- Opera, Google Chrome, & Safari.

Working of Web Browser:

A Web Browser acts as the client in the WWW interaction. Using this program, a user requests for a web page stored on a web server. The web server locates this web page and sends it back to the client computer. The web browser then interprets the web page written in the HTML language/format and then displays it on the client computer‘s screen.

Following figure shows the working of web browser-

Search Engines:

While popular sites are well covered by most all of the portals, directories and search engines, individual pages and lesser known sites are not. None are comprehensive and there is not always overlap between the search engines. Sometimes, it is more effective to switch to another search engine rather than to stick just to one. The search engines have many aspects in common, but they also each differ in important ways. Here are some reasons for using specific search engines.

Google: One of the largest and certainly the most popular and best known. Includes cached copies of the page as it appeared when indexed. Also have news, books, groups, image, Maps and scholar databases.

. Yahoo!: One of the largest databases and may find very specific items not found on other search engines. Has advanced search capabilities. Also have image, multimedia and news databases.

Bing: Also one of the largest, and sometimes freshest, databases. Also have image, multimedia, maps, and news databases. The default search engine in Internet Explorer in bing.

Advanced Searching Tips:

Use ―phrase searching‖ whenever possible Add more words to focus results Use a + to turn off stemming, synonyms, and near matches Limit to .edu or .gov to exclude most ecommerce sites



Use link search to find who links to a specific page.

The following list provides a guideline for you to follow in formulating search request, viewing search results, and modifying search results.

1) Identify the important concepts of your search. 2) Choose the keywords that describe these concepts.

3) Determine whether there are synonyms, related terms, or their variations of the

keywords that should be included.

4) Determine which search features may apply, including truncation, proximity operations, Boolean operators, and so forth.

5) Choose a search engine.

6) Read the search instructions on the search engine‘s home page. Look for sections entitled ―Help,‖ ―Advanced Search,‖ ―Frequently Asked Questions,‖ and so forth.

7) Create a search expression, using syntax, which is appropriate for the search engine.

8) Evaluate the results. How many hits were returned? Were the results relevant to your query?

9) Modify your search if needed. Go back to steps 2-4 and revise your query accordingly. 10) Try the same search in a different search engine, following steps 5-9 above.

Search Fundamentals – Basic Indexing:

Successful searching combines creative guessing of URLs along with smart use of subject directories and search engines.

Why Index? Wherever we find a search engine, we also find a set of documents. You‘re lucky if your set is

small, but if it is small enough you can probably scan it by hand. If you need a search engine,

chances are your document collection is big and if you‘re looking at writing a search engine for

the web, it is very, very big. It is ludicrous to expect a search engine to scan all the documents

every time you do a query, it would take forever. To make your queries fast and efficient a

search engine will pre-process the documents and create an index.

The Heart of Ever Search Engine:

At the core of every modern search engine is an inverted index, this is a standard term the reason

for which will become clear shortly. We can assign a set of ids to our documents and then associate

all the words that occur in a particular document with its id, this is rather inefficient for obvious

reasons (duplicate words and all). Instead we invert the concept. We take all the words/terms that

occur in all the documents in our collection – this is called a vocabulary (also standard

terminology) – we then map each term to a set of document ids it occurs in. Each document id is

called a posting and a set of document ids is a postings list. So, the most basic inverted index is a

dictionary of terms each of which is associated with a postings list. 5) go through all the documents, assign each an id and tokenize each one for words

6) process all the tokens (linguistic processing), to produce a list of normalized tokens

7) for each token create a postings list, i.e. a list of document ids it occurs in



Of course those 3 simple steps hide infinite layers of complexity. What we want to end up with

is a sorted list of terms each of which is associated with a list of document ids. We can also

start storing some extra info even with this basic inverted index, such as the document

frequency for each term (how many documents the term occurs in). This extra information will

eventually become useful when we want to rank our search results.

Search Strategies:

Successful searching involves two key steps.

1) You must have a clear understanding of how to prepare your search. You must identify the main concepts in your topic and determine any synonyms, alternate spellings, or variant word forms for concepts.

2) You need to know how to use the various search tools available on the Internet. For

example, search engines are very different than subject directories. Even search engines themselves can vary greatly in size, accuracy, features and flexibility.

There are three basic types of search tools that most people use to find what they are looking for on the Web-

Search Engines

Search engines are large, spider created databases of web pages that help searchers find specific information on any given subject. You type in a keyword or phrase and the search engine retrieves pages that correspond to your search query.

Search results gathered from these search engines are not always relevant to the keywords entered, since these engines are not intuitive and cannot infer dynamically what it is you might be searching for.

Subject Directories

Subject directories in general are more smaller and selective that search engines. They use categories to focus your search, and their sites are arranged by categories, not just by keywords. Subject directories are handy for broad searches, as well as finding specific websites. Most subject directories‘ main purpose is to be informational, rather than commercial. A good example of a search directory is Yahoo, a combination search engine/search directory/search portal, or one of the original search directories, Open Directory or DMOZ for short.

MetaSearch Tools

Metasearch engines get their search results from several search engines. Users will receive the best hits to their keywords from each search engine. Metasearch tools are a good place to start for very broad results, but do not give the same quality results as using each search engine and directory.

Meta Search Engines:

Search with multiple search engines at the same time with metasearch engines, unique tools you can use to scour more of the Web. Here are some metasearch engines discussed below:

1) Dogpile:



Dogpile, a meta search engine, isa great way to compare and compile results from many different search engines and directories at the same time.

2) Clusty:

A meta search engine with lots of interesting features, including a blogosphere meta search option, customization tabs and of course clustering.

3) ZapMeta:

A great search engine that delivers fast, relevant result with plenty of extra search features such as Quick View, results snapshot and advanced relevance filtering.

4) Kartoo:

Kartoo is a different breed of search engine- all your results are presented in a unique visual format: instead of text results, you get an interactive map.

5) Mamma:

Mamma.com is a good, solid meta search engine that provides fast and relvant results and excellent advanced search options.

6) Search:

Search.com is one of best meta search engines. Not only does search.com offer you the standard meta search experience of retrieving results from multiple search engines, they also offer minimeta search engines on a variety of specific topics; anything from Blogs to Gaming to Bussiness.

7) Lxquick:

It pulls results from many different search engines and directories and presents them all in one simple search results page. Lxquick ease to use, relevant results.



Web Servers:

A web server is a piece of software that enables a website to be viewed using HTTP. Web server can refer to either the hardware (the computer) or the software (the computer application) that helps to deliver content that can be accessed through the Internet.

The primary function of a web server is to deliver web pages on the request to clients. This means delivery of HTML documents and any additional content that may be included by a document, such as images, style sheets and scripts.

Web servers are not always used for serving the world wide web. They can also be found embedded in devices such as printers, routers, webcams and serving only a local network. The web server may then be used as a part of a system for monitoring and/or administrating the device in question. This usually means that no additional software has to be installed on the client computer; since only a web browser is required (which now is included with most operating systems).

History of Web Server:

In 1989 Tim Berners-Lee proposed a new project with the goal of easing the exchange

of information between scientists by using a hypertext system to his employer CERN.

The project resulted in Berners-Lee writing two programs in 1990: 3) A browser called WorldWideWeb

4) The world's first web server, later known as CERN httpd, which ran on NeXTSTEP

Between 1991 and 1994, the simplicity and effectiveness of early technologies used to surf

and exchange data through the World Wide Web helped to port them to many different

operating systems and spread their use among socially diverse groups of people, first in

scientific organizations, then in universities and finally in industry.



In 1994 Tim Berners-Lee decided to constitute the World Wide Web Consortium (W3C) to

regulate the further development of the many technologies involved (HTTP, HTML, etc.)

through a standardization process.

Advantages of Web Server:

Here are some advantages of using a web server within your development environment:

Your local website behaves more like the live one. For example, you can configure directory security; test your custom error pages etc before committing them to the production environment.

You can use server-side scripting languages such as PHP and ColdFusion.

Allows you to standardize your coding. For example, you can use root-relative paths for your image references and hyperlinks (i.e. "/directory/image.gif"). In other words, your paths can represent the website structure, rather than the directory structure of your computer.

Knowledge. The knowledge you gain from using your own web server will help you understand how it works in the live environment. This will most certainly help you when you need to communicate with your hosting provider - you'll be able to use terminology that makes it easier for them to understand your request/issue.

Web Server features:

Most web servers have features that allow you to do the following:

Create one or more websites. (No I don't mean build a set of web pages. What I mean is, set up the website in the web server, so that the website can be viewed via HTTP)

Configure log file settings, including where the log files are saved, what data to include on the log files etc. (Log files can be used to analyze traffic etc)

Configure website/directory security. For example, which user accounts are/aren't allowed viewing the website, which IP addresses are/aren‘t, allowed to view the website etc.

Create an FTP site. An FTP site allows users to transfer files to and from the site.

Create virtual directories, and map them to physical directories

Configure/nominate custom error pages. This allows you to build and display user friendly error messages on your website. For example, you can specify which page is displayed when a user tries to access a page that doesn't exist (i.e. a "404 error").

Specify default documents. Default documents are those that are displayed when no file

name is specified. For example, if you open "http://localhost", which file should be

displayed? This is typically "index.html" or similar but it doesn't need to be. You could



nominate "index.cfm" if your website is using ColdFusion. You could also nominate a 2nd choice (in case there is no index.cfm file), and a 3rd choice, and so on.

Internet Information Services (IIS):

IIS (Internet Information Server) is a group of Internet servers (including a Web or Hypertext

Transfer Protocol server and a File Transfer Protocol server) with additional capabilities for

Microsoft's Windows NT and Windows 2000 Server operating systems. IIS is Microsoft's entry

to compete in the Internet server market that is also addressed by Apache, Sun Microsystems,

O'Reilly, and others. With IIS, Microsoft includes a set of programs for building and

administering Web sites, a search engine, and support for writing Web-based applications that

access database.

Apache:

The Apache HTTP Server commonly referred to as Apache, is web server software notable

for playing a key role in the initial growth of the World Wide Web. In 2009 it became the first

web server software to surpass the 100 million website milestone. Apache was the first viable

alternative to the Netscape Communications Corporation web server (currently named Oracle

iPlanet Web Server), and since has evolved to rival other web servers in terms of functionality

and performance. Typically Apache is run on a Unix-like operating system.

Apache is developed and maintained by an open community of developers under the auspices

of the Apache Software Foundation. The application is available for a wide variety of operating

systems, including Unix, FreeBSD, Linux, Solaris, Novell NetWare, AmigaOS, Mac OS X,

Microsoft Windows, OS/2,TPF, and eComStation. Released under the Apache License,

Apache is open-source software.

Apache was originally based on NCSA HTTP code. The NCSA code has since been removed from Apache, due to a rewrite.

Since April 1996 Apache has been the most popular HTTP server software in use. As of May 2011 Apache was estimated to serve 63% of all websites and 66% of the million busiest.

Configuring Web Server:

Installing IIS Web Server on your computer:

1. Open Control Panel



2. Click on Add/Remove programs

3) Click on Add/Remove Windows Components

4) You will see the Windows Components Wizard. Tick the box next to Internet Information Services (IIS)

5) Click on the Next button 6) You will be asked to insert your Windows XP installer disk

7) The setup Wizard will copy and install the necessary files from the CD.

NOTE: If the Windows XP Installer screen appears (which auto-runs from the Installer CD), click on the Exit button

8) After a few minutes you will be advised that the IIS components have been installed



9) Click on the Finish button

10) Close the Add/Remove Software window

Setting up your own web site:

1. Open the Control Panel from the Start menu

2. Click on Performance and Maintenance.

3. Click on Administrative Tools.

4. Click on Internet Information Services.



5. Expand the ―tree‖ in the left column to display the Default Web Site.

6. Right click on the Default Web Site and choose Properties. 7. Click on the Home Directory tab and specify the new location of the default web folder.

8. If your ―default‖ web page, with the Intranet folder, has an ―html‖ extension,

click on the Documents tab.



Add index.html as a default document. 9. Click on the Apply button, and the OK button.

10. Move to a network computer. Open a browser and enter the IP address of the web

server. You will see your default web page!

.
