It302 Prelim Topics

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Introduction to

Software Engineering

Introduction to

Software Engineering



College of Computer StudiesCollege of Computer Studies

Computer programs and associated documentation suchas requirements, design models and user manuals.

Software products may be developed for a particular customer or may be developed for a general market.

Software products may be ± Generic - developed to be sold to a range of different customers

e.g. PC software such as Excel or Word.

± Bespoke (custom) - developed for a single customer accordingto their specification.

New software can be created by developing newprograms, configuring generic software systems or reusing existing software.

Computer programs and associated documentation suchas requirements, design models and user manuals.

Software products may be developed for a particular customer or may be developed for a general market.

Software products may be ± Generic - developed to be sold to a range of different customers

e.g. PC software such as Excel or Word.

± Bespoke (custom) - developed for a single customer accordingto their specification.

New software can be created by developing newprograms, configuring generic software systems or reusing existing software.

What is software?What is software?




Software engineering is an engineeringdiscipline that is concerned with allaspects of software production.

Software engineers should adopt asystematic and organised approach totheir work and use appropriate tools andtechniques depending on the problem tobe solved, the development constraintsand the resources available.

Software engineering is an engineeringdiscipline that is concerned with allaspects of software production.

Software engineers should adopt asystematic and organised approach totheir work and use appropriate tools andtechniques depending on the problem tobe solved, the development constraintsand the resources available.

What is software engineering?What is software engineering?




Computer science is concerned withtheory and fundamentals; softwareengineering is concerned with the

practicalities of developing and deliveringuseful software.

Computer science theories are stillinsufficient to act as a complete

underpinning for software engineering(unlike e.g. physics and electricalengineering).

Computer science is concerned withtheory and fundamentals; softwareengineering is concerned with the

practicalities of developing and deliveringuseful software.

Computer science theories are stillinsufficient to act as a complete

underpinning for software engineering(unlike e.g. physics and electricalengineering).

What is the difference between software

engineering and computer science?


engineering and computer science?




System engineering is concerned with allaspects of computer-based systemsdevelopment including hardware,software and process engineering.

Software engineering is part of thisprocess concerned with developing thesoftware infrastructure, control,applications and databases in thesystem.

System engineers are involved in systemspecification, architectural design,integration and deployment.

System engineering is concerned with allaspects of computer-based systemsdevelopment including hardware,software and process engineering.

Software engineering is part of thisprocess concerned with developing thesoftware infrastructure, control,applications and databases in thesystem.

System engineers are involved in systemspecification, architectural design,integration and deployment.


engineering and system engineering?


engineering and system engineering?




A set of activities whose goal is thedevelopment or evolution of software.

Generic activities in all softwareprocesses are: ± Specification - what the system should do

and its development constraints ± Development - production of the software

system

± Validation - checking that the software iswhat the customer wants ± Evolution - changing the software in

response to changing demands.

A set of activities whose goal is thedevelopment or evolution of software.

Generic activities in all softwareprocesses are: ± Specification - what the system should do

and its development constraints ± Development - production of the software

system

± Validation - checking that the software iswhat the customer wants ± Evolution - changing the software in

response to changing demands.

What is a software process?What is a software process?




A simplified representation of a software process,

presented from a specific perspective.

Examples of process perspectives are

± Workflow perspective - sequence of activities;

± Data-flow perspective - information flow;

± Role/action perspective - who does what.

Generic process models

± Waterfall;

± Iterative development; ± Component-based software engineering.

A simplified representation of a software process,

presented from a specific perspective.

Examples of process perspectives are

± Workflow perspective - sequence of activities;

± Data-flow perspective - information flow;

± Role/action perspective - who does what.

Generic process models

± Waterfall;

± Iterative development; ± Component-based software engineering.

What is a software process model?What is a software process model?




Structured approaches to software development whichinclude system models, notations, rules, design adviceand process guidance.

Model descriptions

± Descriptions of graphical models which should be produced; Rules

± Constraints applied to system models;

Recommendations ± Advice on good design practice;

Process guidance ± What activities to follow.

Structured approaches to software development whichinclude system models, notations, rules, design adviceand process guidance.

Model descriptions

± Descriptions of graphical models which should be produced; Rules

± Constraints applied to system models;

Recommendations ± Advice on good design practice;

Process guidance ± What activities to follow.

What are software engineering methods?What are software engineering methods?




Software systems that are intended to provide

automated support for software process activities.

CASE systems are often used for method support.

Upper-CASE

± Tools to support the early process activities of requirements and

design;

Lower-CASE

± Tools to support later activities such as programming, debugging

and testing.

Software systems that are intended to provide

automated support for software process activities.

CASE systems are often used for method support.

Upper-CASE

± Tools to support the early process activities of requirements and

design;

Lower-CASE

± Tools to support later activities such as programming, debugging

and testing.

What is CASE (Computer-Aided Software

Engineering)

What is CASE (Computer-Aided Software

Engineering)




The software should deliver the required functionalityand performance to the user and should bemaintainable, dependable and acceptable.

Maintainability

± Software must evolve to meet changing needs; Dependability

± Software must be trustworthy;

Efficiency ± Software should not make wasteful use of system resources;

Acceptability ± Software must accepted by the users for which it was designed.

This means it must be understandable, usable and compatiblewith other systems.

The software should deliver the required functionalityand performance to the user and should bemaintainable, dependable and acceptable.

Maintainability

± Software must evolve to meet changing needs; Dependability

± Software must be trustworthy;

Efficiency ± Software should not make wasteful use of system resources;

Acceptability ± Software must accepted by the users for which it was designed.

This means it must be understandable, usable and compatiblewith other systems.

What are the attributes of good software?What are the attributes of good software?




Heterogeneity, delivery and trust.

Heterogeneity

± Developing techniques for building software that can cope with

heterogeneous platforms and execution environments;

Delivery

± Developing techniques that lead to faster delivery of software;

Trust

± Developing techniques that demonstrate that software can be

trusted by its users.

Heterogeneity, delivery and trust.

Heterogeneity

± Developing techniques for building software that can cope with

heterogeneous platforms and execution environments;

Delivery

± Developing techniques that lead to faster delivery of software;

Trust

± Developing techniques that demonstrate that software can be

trusted by its users.

What are the key challenges facing software

engineering?

What are the key challenges facing software

engineering?



IS PROJECT

REASONS

IS PROJECT

REASONS




REASONS FOR INFORMATION SYSTEM PROJECTREASONS FOR INFORMATION SYSTEM PROJECT

The starting point for a project is called aThe starting point for a project is called asystems request, which is a formal way of askingsystems request, which is a formal way of asking

for IT

supportfor IT

support.. A systems request might propose enhancementsA systems request might propose enhancementsfor an existing system, the correction of problems,for an existing system, the correction of problems,or the development of an entirely new informationor the development of an entirely new informationsystem.system.

reasons for systems requests are improvedreasons for systems requests are improvedservice to customers, better performance, moreservice to customers, better performance, moreinformation, stronger controls, and reduced cost.information, stronger controls, and reduced cost.

REASONS FOR INFORMATION SYSTEM PROJECTREASONS FOR INFORMATION SYSTEM PROJECT

The starting point for a project is called aThe starting point for a project is called asystems request, which is a formal way of askingsystems request, which is a formal way of asking

for IT

supportfor IT

support.. A systems request might propose enhancementsA systems request might propose enhancementsfor an existing system, the correction of problems,for an existing system, the correction of problems,or the development of an entirely new informationor the development of an entirely new informationsystem.system.

reasons for systems requests are improvedreasons for systems requests are improvedservice to customers, better performance, moreservice to customers, better performance, moreinformation, stronger controls, and reduced cost.information, stronger controls, and reduced cost.

INFORMATION SYSTEMSINFORMATION SYSTEMS

PROJECTPROJECT




Improved Service: Systems requests often

are aimed at improving service to customers

or users within the company .` check their account balances on a Web site

` storing data on rental car customer

preferences

` or creating an online college registrationsystem

Improved Service: Systems requests often

are aimed at improving service to customers

or users within the company .` check their account balances on a Web site

` storing data on rental car customer

preferences

` or creating an online college registrationsystem

REASONS FOR INFORMATIONREASONS FOR INFORMATION

SYSTEM PROJECTSYSTEM PROJECT




More Information: The system might

produce information that is insufficient,

incomplete, or unable to support thecompany's changing information needs.

` system that tracks customer orders might not

be capable of analysing and predicting

marketing trends

More Information: The system might

produce information that is insufficient,

incomplete, or unable to support thecompany's changing information needs.

` system that tracks customer orders might not

be capable of analysing and predicting

marketing trends






Stronger Controls: A system must have effective

controls to ensure that data is accurate and secure.

common controls include passwords, various levelsof user access and encryption, or coding of data

Sophisticated controls include devices that scan a

person¶s retina to use it as a fingerprint

If a system requires redundant data input or takes toolong to verify every data item, internal users and

customers might complain that the system is not user-

friendly






Reduced Cost: The current system could be

expensive to operate or maintain as a result of

technical problems, design weaknesses, or the

changing demands of the business.






Better Performance: The current system

might not meet performance requirements.

`slow to data inquiries at certain times

` unable to support company growth

` performance limitations also result when a

system that was designed for a specific hardware

configuration becomes obsolete when newhardware is introduced.

Better Performance: The current system

might not meet performance requirements.

`slow to data inquiries at certain times

` unable to support company growth

` performance limitations also result when a

system that was designed for a specific hardware

configuration becomes obsolete when newhardware is introduced.





College of Computer StudiesCollege of Computer StudiesCS211

FACTORS AFFECTING SYSTEMS PROJECTSFACTORS AFFECTING SYSTEMS PROJECTS

User Requests: As users rely more heavily on

information systems to perform their jobs, they are likelyto request even more IT services and support.

sales reps might request improvements to thecompany's Web site

a network to link all sales locations

online system that allows customers to obtain the status

of their orders instantly





Top Management Directives: Directives from topmanagers are a prime source of major systems projects.

Existing Systems: Errors or problems in existingsystems can trigger requests for systems projects.




FACTORS AFFECTING SYSTEMS PROJECTSFACTORS AFFECTING SYSTEMS PROJECTSFACTORS AFFECTING SYSTEMS PROJECTSFACTORS AFFECTING SYSTEMS PROJECTS

Information Technology Department: Many

systems project requests come from the IT

department.

IT proposals might be strictly technical

matters, such as replacement of certain

network components, or suggestions might be

more business oriented, such as proposing anew reporting, or data collection system.

Information Technology Department: Many

systems project requests come from the IT

department.

IT proposals might be strictly technical

matters, such as replacement of certain

network components, or suggestions might be

more business oriented, such as proposing anew reporting, or data collection system.




Economy: Economic activity has a powerful influence oncorporate information management.

In a period of economic expansion, firms need to be ready

with scalable systems that can handle additional volume and

growth.

Technology: Changing technology is a basic force in businessand society in general.

Government: Federal, state, and local government regulationsaffect the design of corporate information systems.





Software And Hardware Vendors: Most companies have amix of software and hardware that must work together to

support information systems requirements.

Customers: Customer service is vitally important, andinformation systems that interact with customers receive top

priority in most firms.





FACTORS AFFECTING SYSTEMS PROJECTSFACTORS AFFECTING SYSTEMS PROJECTSFACTORS AFFECTING SYSTEMS PROJECTSFACTORS AFFECTING SYSTEMS PROJECTS

Competitors: Customer service is vitally

important, and information systems that

interact with customers receive top


Suppliers: With the growth of electronicdata interchange (EDI), relationships with

suppliers are critically important.

Competitors: Customer service is vitally

important, and information systems that

interact with customers receive top


Suppliers: With the growth of electronicdata interchange (EDI), relationships with

suppliers are critically important.



SDLC PHASESSDLC PHASES




PLANNING PHASEPLANNING PHASEProject Planning Phase Activities Key Questions

Define the problem Do we understand what we are supposed to be

working on?

Produce the project schedule Can the project be completed on time given the

available resources?

Confirm project feasibility Is it still feasible to begin working on this project?

Staff the project Are the resources available, trained, and ready to

start the project?

Launch the project Are we ready to start the project?




OVERVIEW OFOVERVIEW OF FEASIBILITYFEASIBILITY

A systems request must meet several tests to see whether it

is worthwhile to proceed further. A feasibility study uses

three major yardsticks to measure, or predict a system's

success: operational feasibility, technical feasibility, and

economic feasibility.






System request must pass an initial review to decidewhether it deserves further study.

3 IMPORTANT QUESTIONS:

1. Is the proposal desirable in an operational sense? Is ita practical approach that will solve a problem or takeadvantage of an opportunity to achieve companygoals?

2. Is the proposal technically feasible? Are the necessarytechnical resources and people available for theproject?

3. Is the proposal economically desirable?

What are the projected savings and costs?

Are there other intangible factors, such as customer satisfaction or company image?

Is the problem worth solving, and will the requestresult in a sound business investment?

Is the proposal economically desirable?

System request must pass an initial review to decidewhether it deserves further study.

3 IMPORTANT QUESTIONS:

1. Is the proposal desirable in an operational sense? Is ita practical approach that will solve a problem or takeadvantage of an opportunity to achieve companygoals?

2. Is the proposal technically feasible? Are the necessarytechnical resources and people available for theproject?

3. Is the proposal economically desirable?

What are the projected savings and costs?

Are there other intangible factors, such as customer satisfaction or company image?

Is the problem worth solving, and will the requestresult in a sound business investment?

Is the proposal economically desirable?




Does the company have the necessary hardware,

software, and network resources?

Does the company have the needed technical

expertise? If not, can it be acquired?

Does the company have the necessary hardware,

software, and network resources?

Does the company have the needed technical

expertise? If not, can it be acquired?

Technical Feasibility: A systems request has

technical feasibility if the organization has the

resources to develop or purchase, install, and

operate the system.






analyst needs to estimate costs in each of the following area:

People, including IT staff and users

Hardware and equipment

Software, including in-house development as well as

purch

ases from vendor Formal and informal training

Licenses and fees

Consulting expenses

Facility costs

assess tangible and intangible benefits to the company

analyst needs to estimate costs in each of the following area:

People, including IT staff and users

Hardware and equipment

Software, including in-house development as well as

purch

ases from vendor Formal and informal training

Licenses and fees

Consulting expenses

Facility costs

assess tangible and intangible benefits to the company



Analysis Phase:

Requirements Modelling

Analysis Phase:

Requirements Modelling




SYSTEMS ANALYSISSYSTEMS ANALYSIS

PHASE OVERVIEWPHASE OVERVIEW

The systems analysis phase includes the four activities:requirements modelling, data and process modelling,

object modelling, and the transition to systems design.




SYSTEM REQUIREMENTSSYSTEM REQUIREMENTS

CHECKLISTCHECKLIST

System requirements fall into five general categories:

outputs, inputs, processes, performance, and

controls.

Typical examples of system requirements are:

Outputs

The Web site must report online volume statistics

every four hours, and hourly during peak periods.




Inputs

A data entry person at the medical group must input

patient services into the billing system.

Processes The human resources system must interface properly

with the existing payroll system.




Performance

The system must be operational 7 days a

week, 365 days a year.Controls

The system must provide log-on security

at the operating system level and at theapplication level.

Performance

The system must be operational 7 days a

week, 365 days a year.Controls

The system must provide log-on security

at the operating system level and at theapplication level.



College of

Computer Studies

College of

Computer StudiesCS211

FACTFACT--FINDINGFINDING

WHO, WHAT, WHEN, WHERE AND HOW?

Fact-finding involves answers to five familiar

questions: who, what, when, where, and how.

1.Who? Who performs each of the procedures

within the system?

2.What? What is being done?

3.Where? Where are operations being performed?

4.When? When is a procedure performed?5.How? How is a procedure performed?



College of

Computer Studies

College of


FACTFACT--FINDINGFINDING TECHNIQUESTECHNIQUES

INTERVIEWSThe interviewing process consists of these seven steps:

1. Determine the people to interview.

2. Establish objectives for the interview.

3. Develop interview questions.4. Prepare for the interview.

5. Conduct the interview.

6. Document the interview.

7. Evaluate the interview.



College of

Computer Studies

College of

Computer Studies

Document Review

Obtain copies of actual forms and

operating documents currently in use.Review blank copies of forms, as well

as samples of actual completed forms.

Document Review

Obtain copies of actual forms and

operating documents currently in use.Review blank copies of forms, as well

as samples of actual completed forms.



College of

Computer Studies

College of

Computer Studies

Observation

Personal observation also allows

you to verify statements made ininterviews and determine whether

procedures really operate as they

are described.

Observation

Personal observation also allows

you to verify statements made ininterviews and determine whether

procedures really operate as they

are described.



College of

Computer Studies

College of


Questionnaires and Surveys

A questionnaire, also called a survey, is a

document containing a number of standardquestions that can be sent to many individuals.



College of

Computer Studies

College of

Computer Studies

Sampling

The samples include records, reports, operationallogs, data entry documents, complaint summaries,

work requests, and various types of forms.Sampling techniques include:

systematic sampling - select every tenthcustomer for review

stratified sampling - select five customers fromeach of four ZIP codes

random sampling

Sampling

The samples include records, reports, operationallogs, data entry documents, complaint summaries,

work requests, and various types of forms.Sampling techniques include:

systematic sampling - select every tenthcustomer for review

stratified sampling - select five customers fromeach of four ZIP codes

random sampling



College of

Computer Studies

College of


RESEARCHRESEARCH

another important fact-finding technique

include reviewing journals

periodicals and books to obtain

background information technical material

news about industry trends and

developments

Research also can involve site visits

another important fact-finding technique

include reviewing journals

periodicals and books to obtain

background information technical material

news about industry trends and

developments

Research also can involve site visits



College of

Computer Studies

College of

Computer Studies

As an analyst, you should select the technique that

will work best in a particular situation.

It302 Prelim Topics

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