week 1 - introduction (se)

8/20/2019 Week 1 - Introduction (SE)

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Chapter 1- Introduction

Lecture 1



Topics covered

TDB21632

Professional software development What is meant by software engineering.

Software engineering ethics A brief introduction to ethical issues that aect

software engineering. Case studies An introduction to three examples that are used in

later chapters in the book.

Week 1



Software engineering

he economies of A!! developed nations aredependent on software.

"ore and more systems are softwarecontrolled

Software engineering is concerned withtheories# methods and tools for professionalsoftware development.

$xpenditure on software represents a

signi%cant fraction of &'P in all developedcountries.

Week 1TDB21633



Software costs

Software costs often dominate computersystem costs. he costs of software on a PCare often greater than the hardware cost.

Software costs more to maintain than it does

to develop. (or systems with a long life#maintenance costs may be several timesdevelopment costs.

Software engineering is concerned with cost)

eective software development.

Week 1TDB21634



Software products

TDB21635

&eneric products Stand)alone systems that are marketed and sold

to any customer who wishes to buy them.

$xamples * PC software such as graphicsprograms# pro+ect management tools, CA-software, software for speci%c markets such asappointments systems for dentists.

Customied products Software that is commissioned by a speci%c

customer to meet their own needs.

$xamples * embedded control systems# air tra/ccontrol software# tra/c monitoring systems.

Week 1



Product specification

TDB21636

&eneric products he speci%cation of what the software should do is

owned by the software developer and decisions onsoftware change are made by the developer.

Customied products he speci%cation of what the software should do is

owned by the customer for the software and theymake decisions on software changes that arere0uired.

Week 1



Frequently asked questions about softwareengineering

TDB21637

Question Answer

What is software? Computer programs and assoiated doumentation!"oftware produts ma# $e de%e&oped for a partiu&arustomer or ma# $e de%e&oped for a genera& market!

What are the attri$utes of good software? 'ood software shou&d de&i%er the re(uired funtiona&it#

and performane to the user and shou&d $emaintaina$&e) dependa$&e and usa$&e!

What is software engineering? "oftware engineering is an engineering disip&ine that isonerned with a&& aspets of software prodution!

What are the fundamenta& softwareengineering ati%ities?

"oftware speifiation) software de%e&opment) software%a&idation and software e%o&ution!

What is the differene $etween software

engineering and omputer siene?

Computer siene fouses on theor# and fundamenta&s*

software engineering is onerned with the pratia&itiesof de%e&oping and de&i%ering usefu& software!

What is the differene $etween softwareengineering and s#stem engineering?

"#stem engineering is onerned with a&& aspets ofomputer+$ased s#stems de%e&opment in&udinghardware) software and proess engineering! "oftwareengineering is part of this more genera& proess!

Week 1



Frequently asked questions about softwareengineering

TDB2163,

Question Answer

What are the ke# ha&&enges faingsoftware engineering?

Coping with inreasing di%ersit#) demands for reduedde&i%er# times and de%e&oping trustworth# software!

What are the osts of softwareengineering?

-ough&# 6./ of software osts are de%e&opment osts)4./ are testing osts! 0or ustom software) e%o&utionosts often eeed de%e&opment osts!

What are the $est software engineeringtehni(ues and methods?

Whi&e a&& software proets ha%e to $e professiona&&#managed and de%e&oped) different tehni(ues areappropriate for different t#pes of s#stem! 0or eamp&e)games shou&d a&wa#s $e de%e&oped using a series ofprotot#pes whereas safet# ritia& ontro& s#stems re(uirea omp&ete and ana&#a$&e speifiation to $e de%e&oped!ou ant) therefore) sa# that one method is $etter than

another!

What differenes has the we$ made tosoftware engineering?

The we$ has &ed to the a%ai&a$i&it# of software ser%iesand the possi$i&it# of de%e&oping high&# distri$uted ser%ie+$ased s#stems! We$+$ased s#stems de%e&opment has&ed to important ad%anes in programming &anguages andsoftware reuse!

Week 1



Essential attributes of good software

TDB2163

Product characteristic Description

aintaina$i&it# "oftware shou&d $e written in suh a wa# so that it an e%o&%e tomeet the hanging needs of ustomers! This is a ritia& attri$ute$eause software hange is an ine%ita$&e re(uirement of ahanging $usiness en%ironment!

Dependa$i&it# andseurit#

"oftware dependa$i&it# in&udes a range of harateristisin&uding re&ia$i&it#) seurit# and safet#! Dependa$&e softwareshou&d not ause ph#sia& or eonomi damage in the e%ent ofs#stem fai&ure! a&iious users shou&d not $e a$&e to aess ordamage the s#stem!

8ffiien# "oftware shou&d not make wastefu& use of s#stem resoures suhas memor# and proessor #&es! 8ffiien# therefore in&udes

responsi%eness) proessing time) memor# uti&isation) et!

9epta$i&it# "oftware must $e aepta$&e to the t#pe of users for whih it isdesigned! This means that it must $e understanda$&e) usa$&e andompati$&e with other s#stems that the# use!

Week 1



Software engineering

TDB21631.

Software engineering is an engineering disciplinethat is concerned with all aspects of softwareproduction from the early stages of systemspeci%cation through to maintaining the systemafter it has gone into use.

$ngineering discipline 1sing appropriate theories and methods to solve

problems bearing in mind organiational and %nancialconstraints.

All aspects of software production 'ot +ust technical process of development. Also pro+ect

management and the development of tools# methodsetc. to support software production.

Week 1



Importance of software engineering

TDB216311

"ore and more# individuals and society rely onadvanced software systems. We need to beable to produce reliable and trustworthysystems economically and 0uickly.

2t is usually cheaper# in the long run# to usesoftware engineering methods and techni0uesfor software systems rather than +ust write theprograms as if it was a personal programming

pro+ect. (or most types of system# thema+ority of costs are the costs of changing thesoftware after it has gone into use.

Week 1



Software process activities

TDB216312

Software speci%cation# where customers andengineers de%ne the software that is to beproduced and the constraints on its operation.

Software development# where the software is

designed and programmed. Software validation# where the software is

checked to ensure that it is what the customerre0uires.

Software evolution# where the software ismodi%ed to re3ect changing customer andmarket re0uirements.

Week 1



General issues that affect most software

TDB216313

4eterogeneity 2ncreasingly# systems are re0uired to operate as

distributed systems across networks that includedierent types of computer and mobile devices.

5usiness and social change 5usiness and society are changing incredibly

0uickly as emerging economies develop and newtechnologies become available. hey need to beable to change their existing software and to

rapidly develop new software. Security and trust As software is intertwined with all aspects of our

lives# it is essential that we can trust that

software. Week 1



Software engineering diversity

TDB216314

here are many dierent types of softwaresystem and there is no universal set ofsoftware techni0ues that is applicable to all ofthese.

he software engineering methods and toolsused depend on the type of application beingdeveloped# the re0uirements of the customerand the background of the development team.

Week 1



Application types

TDB216315

Stand)alone applications hese are application systems that run on a local

computer# such as a PC. hey include all necessaryfunctionality and do not need to be connected to anetwork.

2nteractive transaction)based applications Applications that execute on a remote computer and are

accessed by users from their own PCs or terminals. heseinclude web applications such as e)commerce applications.

$mbedded control systems

hese are software control systems that control andmanage hardware devices. 'umerically# there are probablymore embedded systems than any other type of system.

Week 1



Application types

TDB216316

5atch processing systems hese are business systems that are designed to

process data in large batches. hey process largenumbers of individual inputs to createcorresponding outputs.

$ntertainment systems hese are systems that are primarily for personal

use and which are intended to entertain the user.

Systems for modeling and simulation hese are systems that are developed by

scientists and engineers to model physicalprocesses or situations# which include many#separate# interacting ob+ects.

Week 1



Application types

TDB216317

-ata collection systems hese are systems that collect data from their

environment using a set of sensors and send thatdata to other systems for processing.

Systems of systems hese are systems that are composed of a numberof other software systems.

Week 1



Software engineering fundamentals

TDB21631,

Some fundamental principles apply to all types ofsoftware system# irrespective of the developmenttechni0ues used6 Systems should be developed using a managed and

understood development process. 7f course# dierent

processes are used for dierent types of software. -ependability and performance are important for all

types of system.

1nderstanding and managing the software speci%cationand re0uirements 8what the software should do9 are

important. Where appropriate# you should reuse software that has

already been developed rather than write newsoftware.

Week 1



Software engineering and the web

TDB21631

he Web is now a platform for runningapplication and organiations are increasinglydeveloping web)based systems rather thanlocal systems.

Web services 8discussed in Chapter :;9 allowapplication functionality to be accessed overthe web.

Cloud computing is an approach to the

provision of computer services whereapplications run remotely on the <cloud=. 1sers do not buy software buy pay according to

use.

Week 1



Web software engineering

TDB21632.

Software reuse is the dominant approach for constructingweb)based systems. When building these systems# you think about how you can

assemble them from pre)existing software components and systems.

Web)based systems should be developed and deliveredincrementally. 2t is now generally recognied that it is impractical to specify all the

re0uirements for such systems in advance.

1ser interfaces are constrained by the capabilities of webbrowsers. echnologies such as A>A? allow rich interfaces to be created within

a web browser but are still di/cult to use. Web forms with localscripting are more commonly used.

Week 1



Web-based software engineering

TDB216321

Web)based systems are complex distributedsystems but the fundamental principles ofsoftware engineering discussed previously areas applicable to them as they are to any othertypes of system.

he fundamental ideas of softwareengineering# discussed in the previoussection# apply to web)based software in the

same way that they apply to other types ofsoftware system.

Week 1



Key points

TDB216322

Software engineering is an engineeringdiscipline that is concerned with all aspects ofsoftware production.

$ssential software product attributes are

maintainability# dependability and security#e/ciency and acceptability.

he high)level activities of speci%cation#development# validation and evolution are partof all software processes.

he fundamental notions of softwareengineering are universally applicable to alltypes of system development.

Week 1



Key points

TDB216323

here are many dierent types of system andeach re0uires appropriate softwareengineering tools and techni0ues for theirdevelopment.

he fundamental ideas of softwareengineering are applicable to all types ofsoftware system.

Week 1



Chapter 1- Introduction

Lecture 2



Software engineering ethics

Software engineering involves widerresponsibilities than simply the application oftechnical skills.

Software engineers must behave in an honest

and ethically responsible way if they are to berespected as professionals.

$thical behaviour is more than simplyupholding the law but involves following a set

of principles that are morally correct.

Week 1TDB216325



Issues of professional responsibility

Con%dentiality $ngineers should normally respect thecon%dentiality of their employers or clientsirrespective of whether or not a formalcon%dentiality agreement has been signed.

Competence $ngineers should not misrepresent their level of

competence. hey should not knowingly acceptwork which is outwith their competence.

Week 1TDB216326



Issues of professional responsibility

2ntellectual property rights $ngineers should be aware of local laws governing the use

of intellectual property such as patents# copyright# etc. hey should be careful to ensure that the intellectualproperty of employers and clients is protected.

Computer misuse Software engineers should not use their technical skills to

misuse other people=s computers. Computer misuseranges from relatively trivial 8game playing on anemployer=s machine# say9 to extremely serious

8dissemination of viruses9.

Week 1TDB216327



ACM/IEEE Code of Ethics

he professional societies in the 1S havecooperated to produce a code of ethicalpractice.

"embers of these organisations sign up to thecode of practice when they +oin.

he Code contains eight Principles related tothe behaviour of and decisions made byprofessional software engineers# includingpractitioners# educators# managers#

supervisors and policy makers# as well astrainees and students of the profession.

Week 1TDB21632,



Rationale for the code of ethics

TDB21632

Computers have a central and growing role in

commerce, industry, government, medicine, education,entertainment and society at large. Software engineersare those who contribute by direct participation or byteaching, to the analysis, specication, design,development, certication, maintenance and testing of

software systems. Because of their roles in developing software systems,

software engineers have signicant opportunities to dogood or cause harm, to enable others to do good orcause harm, or to inuence others to do good or causeharm. To ensure, as much as possible, that their eortswill be used for good, software engineers must committhemselves to maing software engineering a benecialand respected profession.

Week 1



The ACM/IEEE Code of Ethics

TDB21633.

Software Engineering Code of Ethics and Professional Practice

9C:;888+C" <oint Task 0ore on "oftware 8ngineering 8this and =rofessiona& =raties

PREAMBLE

The short %ersion of the ode summaries aspirations at a high &e%e& of the a$stration* the

&auses that are in&uded in the fu&& %ersion gi%e eamp&es and detai&s of how theseaspirations hange the wa# we at as software engineering professiona&s! Without the

aspirations) the detai&s an $eome &ega&isti and tedious* without the detai&s) the

aspirations an $eome high sounding $ut empt#* together) the aspirations and the detai&s

form a ohesi%e ode!

"oftware engineers sha&& ommit themse&%es to making the ana&#sis) speifiation) design)

de%e&opment) testing and maintenane of software a $enefiia& and respeted profession! ;naordane with their ommitment to the hea&th) safet# and we&fare of the pu$&i) software

engineers sha&& adhere to the fo&&owing 8ight =rinip&es>

Week 1



Ethical principles

TDB216331

1! =B@;C + "oftware engineers sha&& at onsistent&# with the pu$&i interest!

2! C@;8AT 9AD 8=@8- + "oftware engineers sha&& at in a manner that is in the $est

interests of their &ient and emp&o#er onsistent with the pu$&i interest!

3! =-DCT + "oftware engineers sha&& ensure that their produts and re&ated

modifiations meet the highest professiona& standards possi$&e!

4! <D'8AT + "oftware engineers sha&& maintain integrit# and independene in their

professiona& udgment!

5! 9A9'88AT + "oftware engineering managers and &eaders sha&& su$sri$e to and

promote an ethia& approah to the management of software de%e&opment and

maintenane!

6! =-08"";A + "oftware engineers sha&& ad%ane the integrit# and reputation of theprofession onsistent with the pu$&i interest!

7! C@@89'8" + "oftware engineers sha&& $e fair to and supporti%e of their o&&eagues!

,! "8@0 + "oftware engineers sha&& partiipate in &ife&ong &earning regarding the pratie of

their profession and sha&& promote an ethia& approah to the pratie of the profession!

Week 1



Ethical dilemmas

-isagreement in principle with the policies ofsenior management.

@our employer acts in an unethical way andreleases a safety)critical system without

%nishing the testing of the system. Participation in the development of military

weapons systems or nuclear systems.

Week 1TDB216332



Case studies

TDB216333

A personal insulin pump An embedded system in an insulin pump used by

diabetics to maintain blood glucose control.

A mental health case patient management

system A system used to maintain records of people

receiving care for mental health problems.

A wilderness weather station

A data collection system that collects data aboutweather conditions in remote areas.

Week 1



Insulin pump control system

TDB216334

Collects data from a blood sugar sensor andcalculates the amount of insulin re0uired to bein+ected.

Calculation based on the rate of change of

blood sugar levels. Sends signals to a micro)pump to deliver the

correct dose of insulin.

Safety)critical system as low blood sugars can

lead to brain malfunctioning# coma and death,high)blood sugar levels have long)termconse0uences such as eye and kidneydamage.

Week 1



Insulin pump hardware architecture

TDB216335 Week 1



Activity model of the insulin pump

TDB216336 Week 1



Essential high-level requirements

TDB216337

he system shall be available to deliver insulinwhen re0uired.

he system shall perform reliably and deliverthe correct amount of insulin to counteract the

current level of blood sugar. he system must therefore be designed and

implemented to ensure that the systemalways meets these re0uirements.

Week 1



A patient information system for mentalhealth care

TDB21633,

A patient information system to support mentalhealth care is a medical information system thatmaintains information about patients suering frommental health problems and the treatments thatthey have received.

"ost mental health patients do not re0uirededicated hospital treatment but need to attendspecialist clinics regularly where they can meet adoctor who has detailed knowledge of theirproblems.

o make it easier for patients to attend# these clinicsare not +ust run in hospitals. hey may also be heldin local medical practices or community centres.

Week 1



MHC-PMS

TDB21633

he "4C)P"S 8"ental 4ealth Care)Patient"anagement System9 is an informationsystem that is intended for use in clinics.

2t makes use of a centralied database of

patient information but has also beendesigned to run on a PC# so that it may beaccessed and used from sites that do not havesecure network connectivity.

When the local systems have secure networkaccess# they use patient information in thedatabase but they can download and use localcopies of patient records when they are

disconnected. Week 1



The organization of the MHC-PMS

TDB216341 Week 1



MHC-PMS key features

TDB216342

2ndividual care management Clinicians can create records for patients# edit the information in

the system# view patient history# etc. he system supports datasummaries so that doctors can 0uickly learn about the keyproblems and treatments that have been prescribed.

Patient monitoring he system monitors the records of patients that are involved in

treatment and issues warnings if possible problems aredetected.

Administrative reporting he system generates monthly management reports showing

the number of patients treated at each clinic# the number ofpatients who have entered and left the care system# number ofpatients sectioned# the drugs prescribed and their costs# etc.

Week 1



MHC-PMS concerns

TDB216343

Privacy 2t is essential that patient information is

con%dential and is never disclosed to anyoneapart from authorised medical sta and thepatient themselves.

Safety Some mental illnesses cause patients to become

suicidal or a danger to other people. Whereverpossible# the system should warn medical sta

about potentially suicidal or dangerous patients. he system must be available when needed

otherwise safety may be compromised and it maybe impossible to prescribe the correct medication

to patients. Week 1



Wilderness weather station

TDB216344

he government of a country with large areas of

wilderness decides to deploy several hundredweather stations in remote areas.

Weather stations collect data from a set ofinstruments that measure temperature and pressure#

sunshine# rainfall# wind speed and wind direction. he weather station includes a number of instruments that

measure weather parameters such as the wind speed anddirection# the ground and air temperatures# the barometricpressure and the rainfall over a B)hour period. $ach of

these instruments is controlled by a software system thattakes parameter readings periodically and manages thedata collected from the instruments.

Week 1



The weather station’s environment

TDB216345 Week 1



Weather information system

TDB216346

he weather station system his is responsible for collecting weather data# carrying

out some initial data processing and transmitting it tothe data management system.

he data management and archiving system his system collects the data from all of the wilderness

weather stations# carries out data processing andanalysis and archives the data.

he station maintenance system his system can communicate by satellite with all

wilderness weather stations to monitor the health of

these systems and provide reports of problems.

Week 1



Key points

Software engineers have responsibilities to theengineering profession and society. hey shouldnot simply be concerned with technical issues.

Professional societies publish codes of conductwhich set out the standards of behaviour

expected of their members. hree case studies are used in the book6

An embedded insulin pump control system

A system for mental health care patient

management A wilderness weather station

week 1 - introduction (se)

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