01 Ch1 Introduction

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Software

Engineering

Introduction


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SE. IntroductionAug-2014

What is software?

Computer programand associateddocumentation.

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Aug-2014 SE. Introduction

Software products may be

developed for a particularcustomer or may be developed fora general market.

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Attributes of good

software?Good software should deliver therequired functionalityandperformanceto the user andshould be maintainable,dependableand usable.

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Essential attributes of

good software

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What is software

engineering?Software engineering is an engineeringdisciplinethat is concerned with all

aspects of software production

Not just technical process ofdevelopment. Also project

management and the development oftools, methodsetc. to supportsoftware production.

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Fundamental software

engineering activitiessoftware specification

customers and engineers define the software that is to be produced and theconstraints on its operation

software development

software is designed and programmed

software validation

software is checked to ensure that it is what the customer requires

software evolution

software is modified to reflect changing customer and market requirements.

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Fundamental software

engineering activitiesAlternative:definingthe software developmentprocessto be used

managingthe development project

describingthe intended software product

designingthe product

implementingthe product

testing(the parts, integrating and whole) of the product

maintainingthe product

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Key challenges facing

software engineering?

increasing diversity, demands forreduced delivery timesanddeveloping trustworthy software.

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Other FAQs

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Software engineering

fundamentalsSome fundamental principles apply to all types of softwaresystem, irrespective of the development techniques used:

Systems should be developed using a managed and understood

development process. Of course, different processes are used fordifferent types of software.

Dependabilityand performanceare important for all types ofsystem.

Understanding and managing the software specificationandrequirements(what the software should do) are important.

Where appropriate, you should reuse software that has alreadybeen developed rather than write new software.

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Application typesStand-alone applications

Interactive transaction-based applications

Embedded control systems

Batch processing systems

Entertainment systems

Systems for modeling and simulation

Data collection systems

Systems of systems

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UML

Why?

Communication effectively

Graphic annotation

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UML

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UML

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Software project

managementActivities involved in ensuring

software is delivered on timeand onschedule and in accordance with therequirements(technical / non-

technical / budget) of the organisationsdevelopingand procuring the software.

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Proj. man. - success

criteriaDeliver the software to the customer at theagreed time.

Keep overall costs within budget.

Deliver software that meets the customersexpectations.

Maintain a happy and well-functioningdevelopment team.

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Risk

A risk is a probability that someadverse circumstance will occur

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Risk

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Risk

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Consider each risk and develop a strategy to manage it

Avoidance strategies

The probability that the risk will arise is reduced;

Minimisation strategies

The impact of the risk on the project or product will bereduced;

Contingency plans

If the risk arises, contingency plans are plans to deal withthat risk;


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Teamwork

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Any work that needs teamwork?

Any work that needs individualwork?

Software development?


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Teamwork

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Most software engineering is a group activity

The development schedule for most non-trivial software projects issuch that they cannot be completed by one person working alone.

A good group is cohesive and has a team spirit. The peopleinvolved are motivated by the success of the group as well asby their own personal goals.

Group interaction is a key determinant of group performance.

Flexibility in group composition is limited

Managers must do the best they can with available people.


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Cost

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Cost vs. price


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Experience-based techniques

The estimate of future effort requirements is based on themanagers experience of past projects and the applicationdomain. Essentially, the manager makes an informed

judgment of what the effort requirements are likely to be.

Algorithmic cost modeling

In this approach, a formulaic approach is used tocompute the project effort based on estimates of productattributes, such as size, and process characteristics, suchas experience of staff involved.


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Method 1

A simply queue simulation 120-400 LoC

The (first release) Encounter game

4-15 queues + 30-90 additional components of comparable size

=> (30+4) x 120 to (90+15) x 400 = 5-42 KLoC

Use graphics costs 1.5 to 4 times more

=> 7.5 170 KLoC

Method 2

A good video game required 5-20 expert programmers for 1-2 years

We invert 1/10

Assume 5-25 LoC/h (fully tested code)

=> 1/10 x (5-25 lines/h) x (5-20 programmers) x (1-2 years) x (48-50 weeks/year) x (35-60 hours/week) = 4.2-300 KLoC

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COCOMO formula - basic

Ex:

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Effort in Person-months = a!

KLOCb

Duration = c

!Effort d = c! ad!KLOC bd

Software Project a b c d

Organic (stand-alone app.) 2.4 1.05 2.5 0.38

Semidetached 3.0 1.12 2.5 0.35

Embedded (integral HW-SW sys.) 3.6 1.20 2.5 0.32


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Software engineering

ethics

Ethics?

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Software engineering involves widerresponsibilitiesthan simply the applicationof technical skills.

Software engineers must behavein anhonestand ethically responsible wayifthey are to be respected as professionals.

Ethical behaviour is more than simplyupholding the lawbut involves following aset of principlesthat are morally correct.

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ACM/IEEE Code of

EthicsThe professional societiesin the US have cooperatedto produce acode of ethical practice.

Membersof these organisations sign up to the codeof practice when they join.

The Codecontains some Principlesrelated to thebehaviourof and decisionsmade by professionalsoftware engineers, including practitioners,educators, managers, supervisors and policy makers,as well as trainees and students of the profession.

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IEEE code of ethics1. to accept responsibilityin making decisions consistent

with the safety, healthand welfareof the public, and todisclosepromptly factors that might endangerthe publicor the environment;

2. to avoid real or perceived conflicts of interest wheneverpossible, and to disclose them to affected parties whenthey do exist;

3. to be honestand realisticin stating claims or estimatesbased on available data;

4. to reject briberyin all its forms;

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IEEE code of ethics5. to improvethe understanding of technology, its

appropriate application, and potentialconsequences;

6. to maintainand improveour technical competenceand to undertake technological tasks for others onlyif qualified by training or experience, or after fulldisclosure of pertinent limitations;

7. to seek, accept, and offerhonest criticismoftechnical work, to acknowledge and correct errors,and to credit properly the contributions of others;

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IEEE code of ethics8. to treatfairlyall persons regardlessof such

factors as race, religion, gender, disability, age,or national origin;

9. to avoid injuring others, their property,reputation, or employmentby false ormalicious action;

10.to assist colleaguesand co-workers in theirprofessional development and to supportthemin following this code of ethics.

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ACM Code of Ethics and

Professional Conduct1.1 Contribute to society and human well-being.1.2 Avoid harm to others.

1.3 Be honest and trustworthy.

1.4 Be fair and take action not to discriminate.

1.5 Honor property rights including copyrights and patent.

1.6 Give proper credit for intellectual property.

1.7 Respect the privacy of others.

1.8 Honor confidentiality.34

ACM SE C d f E hi d


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ACM SE Code of Ethics andProfessional Practice

(short version)PUBLIC - Software engineers shall act consistently with the public interest.CLIENT AND EMPLOYER - Software engineers shall act in a manner that is in the best interests oftheir client and employer consistent with the public interest.

PRODUCT - Software engineers shall ensure that their products and related modifications meet

the highest professional standards possible.

JUDGMENT - Software engineers shall maintain integrity and independence in their professionaljudgment.

MANAGEMENT - Software engineering managers and leaders shall subscribe to and promote anethical approach to the management of software development and maintenance.

PROFESSION - Software engineers shall advance the integrity and reputation of the professionconsistent with the public interest.

COLLEAGUES - Software engineers shall be fair to and supportive of their colleagues.

SELF - Software engineers shall participate in lifelong learning regarding the practice of theirprofession and shall promote an ethical approach to the practice of the profession.

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Summary

Software engineering is an engineering discipline that isconcerned with all aspects of software production.

Essential software product attributes are maintainability,dependability and security, efficiency and acceptability.

The high-level activities of specification, development,validation and evolution are part of all software processes.

The fundamental notions of software engineering areuniversally applicable to all types of system development.

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SummaryThere are many different types of system andeach requires appropriate softwareengineering tools and techniques for theirdevelopment.

The fundamental ideas of softwareengineering are applicable to all types of

software system.

UML - language (communication effectively?)

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SummaryProject management is to ensure thesoftware to be developed as it is

required on schedule and withinbudget

Risk

Planning

Cost estimation

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SummarySoftware engineers haveresponsibilities to the engineering

profession and society. They should notsimply be concerned with technicalissues.

Professional societies publish codes ofconduct which set out the standards ofbehaviour expected of their members.

Documents

01 Ch1 Introduction