web engrg session 2-1

8/8/2019 Web Engrg Session 2-1

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WEB

ENGINEERING

Part II


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What is Web Engineering?

Discussed Last Session:


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Web System Team.Graphic Designers (look and feel)People with library science background

Database designers (optimum way to store the

information that is to be accessed through the

web system)programmers (develop the code)

network security experts (security aspects)computer experts (hardware architecture based

on performance requirements)Web architects (overall architecture for the Web

system that shows how individual parts are puttogether to create the web system), and;people who has the knowledge to plan a web

development project and manage it


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The primary causes of Web-systems failures are

a flawed design and development process, andpoor management of development efforts.

The way we address these concerns is critical to

realizing the Webs full potential.


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The American Heritage Dictionary of the

English Language, (Third Edition) defines

engineering as:

The application of scientific and mathematicalprinciples to practical ends such as the design,

manufacture, and operation of efficient and

economical structures, machines, processes,

and systems.


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The researchers who first proposed the need for an

Engineering approach for developing large complex

web systems defined Web Engineering as follows.

Web Engineeringdeals with the establishmentand use of sound scientific, engineering and

management principles, disciplined and

systematic approaches to the successful

development, deployment and maintenance of high

quality Web-based systems and applications.


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Do we need an Engineering

Approach to developing largecomplex Web Systems?


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Development of large-scale software in the early

70s:

Lack of suitable process models andapplication architectures gave rise to a software

crisis.


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Web Engineering is very similar to SoftwareEngineering?!

There are many similarities between Software

Engineering and Web Engineering; but we also

have to acknowledge the differences.


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The two key attributes of Web systems that distinguish their

development from traditional software development are:

growth of requirements

continual change of information content.

scalable and maintainable: These features cant be added

later.


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What knowledge constitute WebEngineering?


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Web System Development Maturity Model


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WEB SYSTEM DESIGN


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Building and deploying a Web system is a multi-step

process, in which many steps influence one another

and are iterative.

Most Web systems are bound to continuously evolve

and change, to meet the changing/growing needs ofthe organization.

Development requires knowledge and expertise from

many different disciplines.


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We need a sound process for building Websystems that:

Assists us in capturing the changing requirements and

managing the complexity of the development process,

Assists in the integration of the know-how from variousdisciplines,

Facilitates the communication among various members

involved in the development process the development

team, stakeholders and end-users -, and

Supports the continuous evolution and maintenance and

management of the content.


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Deployment of Web systems in their intended

operational environment.One can develop a technically best Web site, but if

it is not properly used for various reasons, it is a

major failure.

Web system have a front end and a back end.Front end is for the public to access

information about the organization.

Back end is for employees of the organizationto manage and up-date the information in the

Web system.


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Web information or electronic-business (e-business)

system in an organization causes a paradigm shift and

can significantly impact on the work and the way various

business processes are carried out.Internal users of the system must be retrained to

enhance their understanding and use of Web and

web-related technologies and to successfully cope

with the transition.Other factors, including reengineering of business

processes, organizational policy, changes to recruitment

and human resources policies in an organization alsocontribute to successful deployment and use of the Web

systems.


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Seven Essential Steps for Successful Web System

Development

1. Understanding the overall function and operational

environment of the systems including the

corporate/business objectives and requirements and clearly

identifying the stakeholders.

2. Identifying and specifying both technical and non-

technical requirements of the stakeholders and the

overall system.

3. Developing an appropriate architecture for the Web-based system that meets those requirements.


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Seven Essential Steps for Successful Web System

Development (cont.)

4. Satisfactorily addressing the non-technical issues, such

as revised/updated business processes, organizational and

management policies, human resources development, and

legal, cultural and social aspects.

5. Identifying sub-projects or sub-processes to implement

the architecture.

6. Developing and implementing the sub-projects.

7. Incorporating appropriate and effective mechanisms to

manage the evolution and change/maintenance.

.


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WEB PROJECT PLANNING

AND MANAGEMENT


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Figure 2: Development Process for Web Systems

Context

Analysis

Process

Model

Product

Model

Sub Project Plans

Web Site / Environment

Development


Maintenance

QualityContro

l&Assurance

Documentation

ProjectMa

nagement


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Context Analysis

The first essential step in developing a Web system

is context analysis.

Understand the major objectives and corporate

requirements of the system, gather informationabout the operational/application environment and

identify the stakeholders. Based on these needs, decide on both the

technical and non-technical requirements

Broader requirements (such as what thesystem should do), and, Specific requirements (such as security,

access control and performance).


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Within the broader context:

Developers have to understand the specific needs associated

with scalability, maintainability, availability andperformance of the system.

Example:

If the information content and the functions of the system aregoing to evolve considerably: It must be scalable.

If the information on the Web site changes frequently: Must

facilitate easy maintainability of information.

If it is critical to ensure very high availability and catering for

very high peak or uncertain demand: Web site to run on

multiple servers with load balancing and other performance

enhancement mechanisms.


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The features such as design for scalability,

maintainability and performance need to be built

into the initial system architecture, as it is

impossible or very hard to add these features ifthe initial architecture does not support it.


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Example:

An E-business Web site that gives product information.

Information about a product (color, price and availability)may appear on many different pages and this information

can change frequently.

If this Web site was designed as static HTML (hypertext

mark-up language) pages, then every time the productinformation changes one has to change each and every

page that contains this information.

If the information about a product is stored in a central

database and the various web pages that contain this

information is dynamically created by extracting the relevant

information from this database, then we only need to

change information in one place to keep the Web site

current.


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Context Analysis:

Identify the broader requirements such as purpose of

the Web site as well as specific requirements such as

maintainability, scalability, performance, quality control

mechanism for information that will be placed on theWeb site and security.

Provides us with sufficient information to decide on the

broader architecture or Product Model of the system.


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Context

Analysis

Process

Model

Product

Model

Sub Project Plans


Development


Maintenance

QualityContro

l&Assurance

Documentation

ProjectMa

nagement


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Product Model

Shows how various components are linked

together to meet those requirements. Should include the overall

1. physical system architecture (the network andthe various servers - web servers, application

servers, database servers, etc),

2. application architecture (a map of the various

information modules and the functions

available) and the

3. software architecture (various software anddatabase modules required to implement the

application architecture).


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Appropriate system architecture is very

important especially if performance andsecurity of the Web system are critical

factors.


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Example:

Web site for 1998 Olympic Winter Games in Nagano,

Japan meeting the performance requirement was acritical factor.

Hence, a network and server architecture that includes

redundant hardware, load balancing, Web server

acceleration, and efficient management of dynamicdata was designed and implemented.

If the performance and security is not a critical issue,

one can use a standard server architecture connected

to the Internet, without the need for special design

effort.


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The application architecture, also called as product

model, shows a map of various information and

functional modules.

Examples of functional modules are a login page,

shopping trolley, etc. that will capture user input and

process it.


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Application architecture of the ABC Internet College

Personalized Tutoring system


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Software Architecture


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Means of Fulfilling the Requirements

Requirement Means of Fulfillment

Corporate look and feel thatcan be changed Create pages using templates

Ensure informationconsistency

Information should be stored in a single place (ina database or an XML

file) without duplication of information.

Need for information updateand maintenance

Provide a back-end system to edit information indata repository

Ability to easily add newpages

Navigation links need to be dynamicallygenerated

Decentralized administration Provide a multiuser login system to access back-

end. Needs a user management system, andability to assign specific functions and data setsto content managers

Quality control mechanism forinformation

Web robot module and metadata standard forWeb pages.


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Context

Analysis

ProcessModel

ProductModel

Sub Project Plans


Development


Maintenance

QualityContro

l&Assurance

Docume

ntation

ProjectMa

nagement


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Process Model

The implementation of the system based on the product model,

calls for a set of activities, which include a detailed analysis of

requirements, design, testing and deployment. We also need to

carry out a set of activities to address the non-technical issues

identified in context analysis.

A process model specifies a set of sub-projects or sub-processes

that need to be carried out to develop and implement the overall

system.

Example: the development of the front-end web site

and the back-end web site can be considered as two sub projects.

This enables parallel development reducing the over all

development time.


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In a large, complex Web application development, the persons

who develop the content generally come from journalism,

library science, marketing or public relations background.

The people who develop the screen layout come from a visual

arts and graphic design background. The software developers

come from computing, software and IT background.

Thus it is important to make sure that the various

processes enable these three groups to work andcommunicate effectively.


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Context

Analysis

ProcessModel

ProductModel

Sub Project Plans


Development


Maintenance

QualityContro

l&Assurance

Docume

ntation

ProjectMa

nagement


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Sub Project Planning

The next phase is to develop a project plan for each of the sub

projects identified in the process model. Project plans should listthe tasks that need to be done, a timeline and the resource

requirements. Based on the project plan, development activities

can take place.

Know the following:

1] tasks required to carry out; 2] people with what type of skills

are required to carry out these tasks; and, 3] the time estimates.

Often the development of front-end Web site and the back-end

web site are done as two sub projects. The coupling of the front-

end web site and the back-end web site will be via the datarepository. In order to properly plan the development of these

Web sites one should know how to develop Web sites.


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Context

Analysis

ProcessModel

ProductModel

Sub Project Plans


Development


Maintenance

QualityContro

l&Assurance

Docume

ntation

ProjectMa

nagement


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Web Site Development

Most Web site development consists of designing the web

site and constructing the web site to deliver the content

and the required functionality.

Early Web development activities were mainly focused on

development of content, its presentation and navigation.

Now, with the growing number of Web based business

applications, there is a need to provide customized

information to users and also to get various information

from the users and process them.


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Experts have developed and refined a two-stage

approach to web site development; designing the

web site and construction of the web site (Figure 5).

This approach decouples the creative design phase

often done by Graphic designers from construction

phase which is often done by software developers. As

often, content developers and software developers

come from different backgrounds, this de-coupling isvery advantageous.


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Figure 5:Two-stage approach to Design and

Construction of Web Sites


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Web Site Design

The web site design process starts with a detailed analysis of

requirements and development of appropriate specification.

A prototype is constructed from the design which usually

contains a set of sample pages that can be used for

evaluating the screen layout and navigation among differentpages. Based on the feedback, either the design or the

specifications can get changed.

One can iterate through this process until stakeholders are

happy with the screen layout and the navigation structure.

The creative part of this process is the design. Figure 6 shows

various inputs to the design process and the typical outcomes

from this process.


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Figure 6: Web Site Design Process


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Once we develop a structure for organizing the

information, we have to decide on navigation

mechanisms that need to be provided to access thiscontent. Access to information can be provided by

hyperlinks or search facility.


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Based on the information structure, we need to

develop sample Web pages to display each type of

information.

Example: If the application is a product catalogue, we

need to develop the Homepage and a sample page for

each product type. These sample pages will act as

templates for creating other product pages which will be

done by application software in response to a user requestwhen web site is operational.

We can use tools such as Dreamweaver or any CMS for

developing these sample pages and the prototype Web

site.

By developing a prototype web site based on sample

pages we can test the proposed navigation mechanisms

for its ease of use and other features.


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If new content needs to be developed, it is better to comeup with guidelines to assist the content development

process as part of the design process.

If content is drawn from a legacy system we need to develop a

process to convert the legacy information to the requiredstructure and format.

The output of the design process and the original

specifications that were developed at the start of the Web

site development process will form the input to the nextstage the web site construction process.


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Web Site Construction

Now, almost every Web server provides a suitable interface to

communicate and to make use of external software modules.

Common Gateway Interface (CGI) was one of the early

standards that was adopted for communication between theweb server and the external software modules.

Today, there are various implementations of this concept in the

form of Application Program Interfaces (API) such as ISAPI

used by the Microsoft IIS Web server.


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Except for simple systems that are based on HTML

pages, every other system makes use of external

software modules to provide the interactivity andcustomization of information provided to the user.

A simple example is processing the information a user

submits via a form. These software modules specifically

developed for these applications are known asapplication software.


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Use of application software enables us to develop

maintainable and scalable Web sites, in addition to

making the Web site interactive.

The basic principle of building a maintainable web site is

not to store data that is going to change with time at

multiple locations.


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We can further enhance the maintainability by developing a

back-end Web site that will enable authorized people (based on

a user ID and a password) to make these changes through a setof forms.

This type of approach will enable us to have a decentralized

maintenance approach where different people can have

responsibility for maintaining different information on the WebSite.


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To facilitate scalability, a Web system needs to be built

using a component- based architecture and the

navigational links and buttons need to be dynamicallycreated.

Use of component-based architecture enables us to

easily add new functions or information modules, by

simply adding these functions as new components.


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Context

Analysis

ProcessModel

ProductModel

Sub Project Plans


Development


Maintenance

QualityControl&Assurance

Docume

ntation

ProjectManagement


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Web Site Maintenance

Once the Web site is developed and commissioned, we enter

then into the maintenance phase. There are three major

types of maintenance:

Content maintenance

Software maintenance, and

Hardware and network maintenance.

The decision on how the content will be maintained is takenat the context analysis stage. Thus what is required at the

maintenance phase is to implement the appropriate content

maintenance procedures.


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The software maintenance can be sub-divided into four

categories: corrective, preventive, perfective and adaptive

maintenance.

Often, when the system is in operation, various bugs in

software can surface. Thus we need to implement a set of

procedures to correct these bugs and document the

changes that were made. This is known as corrective

maintenance.

Also, we invariably come across errors or omissions in

software, especially in the business logic before a problem

occurs. Rectifying these is preventive maintenance.

Though the system may be functioning flawlessly, we may

come up with a better way to implement a function, and the

process of carrying out this modification is known as

perfective maintenance.


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Also, from time to time, the requirements can change

marginally such as how the commission or tax is calculated.

Thus we need to carry out adaptive maintenance to adapt the

system for new business rules.

It is useful to break the software maintenance activities into

these four categories, as this will enable us to prioritize the

activities.


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We also need to periodically maintain the hardware and

the network, and fix the failures as and when theysurface.


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Context

Analysis

ProcessModel

ProductModel

Sub Project Plans


Development


Maintenance

QualityControl&Assurance

Docume

ntation

ProjectManagement


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Project Management, Documentation

and, Quality Control and Assurance

These functions are spread throughout the lifecycle of the

system.

There are well-established methodologies and

techniques to perform these tasks. Proven techniques

used in systems engineering can be used with minor

changes for development of large and complex web sites.


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PROSPECTS OF WEB ENGINEERING

As we improve our ability to build Web systems, the

systems we need to build are likely to get more

complex.

The quality requirements and features of these systems

may also change, with more emphasis on performance,

correctness and availability of Web systems, as we will

increasingly dependent on Web systems in a number of

critical applications, where the consequences and

impact of errors and failures could be serious.


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Further, as systems become larger, a large team of people

with different types and levels of skills would be required,

necessitating distributed collaborative development.

As we try to exploit some of the yet unrealized potentials of

the Internet and Web, there will be many new challenges

and problems, and hopefully new approaches and

directions would be developed to meet the challenges and

solve the problems we may face on our mission to build a

better cyberspace for us.


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Like the Web, which is dynamic and open, Web

engineering needs to evolve rapidly, adapting to the

changes and responding to the newer needs.

Successfully convincing developers of Web applications

about the need for and the benefits of Web engineering

approaches, which if implemented thoughtfully, will go a

long way to reduce the complexity and lead to

successful development.


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Web Engineering

Tools


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Web Engineering Tools

Web Servers APACHE: http://www.apache.orgMicrosoft IIS: http://www.microsoft.com

Image Maps

MapEdit: http://www.boutell.com/mapedit/

MapThis:http://www.abdn.ac.uk/tools/ibmpc/mapthis/


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Menu/Button/Effects Magic Buttons: http://www.pagetutor.com/ JavaScript Maker: http://www.byte-sizesoftware.com/jsc.htm

Applet Glide Navigation Pro:http://www.usingit.com/products/java/applet/agnpro/index.html

Apycom Menu Applets: http://www.apycom.com/apmenu/

Java Tools Javalyzer Java Disassembler:

http://www.bold.net.au/~ianduff/



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Graphics Ulead JavaRazor interactive graphics:

http://www.ulead.com/jr/runme.htm

CrossArtist dynamic digital content:http://www.crossartist.com/

ConeGen VRML2 cone generator:http://www.stack.nl/~vincentn/ConeGen/index.html

StyleSheet Tools xStyle: http: http://www.greenmojo.com/ CSS Style Generator: http://www.10002.org/Download



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CGI Tools CGI Programming Tools:http://www.cgiexpert.com/CGI Mail Form generator:

http://www.lss.com.au/lss/windows/mf/mf_ins.htm

Visual Perl Editor:http://www.xarka.com/vpe.html



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Scripting Tools Nathan Leveck's HTML Parser: http://nl-html-

parser.sourceforge.net/

PHP - Hypertext Preprocessor:http://www.php.net/ PHP Introduction:

http://www.zend.com/zend/art/intro.php COLDFUSION ColdFusion Server - ColdFusion

Studio: http://www.allaire.com

Microsoft Active Server Pages:http://csbs.utsa.edu/users/gjeffery2/doit/



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E-Commerce Tools Gamma GenCat: http://www.gamma-

burst.com/gencat/index.html Auto Search Submitter: http://download.snoop.dk/freew.html

Gate Keeper Security: http://www.pagetutor.com/

Miscellaneous AnalogX CGISearch search authoring:

http://www.analogx.com/ Hot Potatoes multiple choice question writer:

http://web.uvic.ca/hrd/halfbaked/ http://www.winfiles.com http://www.download.com http://www.cookiecentral.com


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