chap8_software engineering

7/21/2019 Chap8_software Engineering

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Copyright © Amity University1

PAN African eNetwork Project

Post Graduate Diploma (IT)

Software Engineering

Semester I

!r" O.P.Sangwan



Copyright © Amity University

Faculty Profile

• Sc !Computer Science"

• CC#A !Cisco certifie$ #etwor% Associate"

• CC#A !Cisco certifie$ "

• Ph & !CS'" !(hesis Su)mitte$"

Pu)lications

* +nternational, #ational -ournal / !inclu$ing AC0 +S-'"

* +nternational, #ational Conference 2 !inclu$ing Springer"Conference, 3or%shop Atten$e$

* 4ang%o%

* 5ietnam




Patents file$ provisionally

* A## mo$el

Area of speciali6ation

* Software 'ngineering

* Artificial +ntelligence

'7perience

* 8 9 teaching

* 1 research

em)er

* Cisco !Aca$emic Council0 USA"

* Cisco !:earning +nstitute0 USA"




3hy 3e #ee$ Software

'ngineering;

• Change in nature < comple7ity of software

• Concept of one =guru> is over

• 3e all want improvement




3hy Software 'ngineering;• Software development is hard ?

• Important to distinguish “easy” systems !onedeveloper, one user, experimental use only " from “hard”systems !multiple developers, multiple users, products"

• Experience with “easy” systems is misleading

* One person techniques do not scale up

• Analogy with bridge building: * Over a stream easy0 one person @o)

* Over iver Severn B ; !the techniques do not scale)



Software Crisis!




Software Crises

As per the IBM report, “31%of theproject get cancelled before the arecopleted, "3% o#er$rn their costestiates b an a#erage of 1&'% andfor e#er 1(( projects, there are ')

restarts*+


http://slidepdf.com/reader/full/chap8software-engineering 8/68Copyright © Amity University

Factors Contri)uting Software Crises

• :arger pro)lems0

• :ac% of a$eDuate training in software

engineering• +ncreasing s%ill shortage0

• :ow pro$uctivity improvements



2

Some Software failures

It too the -ropean Space Agenc 10 yearsand $7 billion to prodce Ariane ", a giantrocet capable of hrling a pair of three$tonsatellites into orbit with each lanch andintended to gi#e -rope o#erwhelingspreac in the coercial space bsiness+

Ariane "

.he rocet was destroed after 3' seconds ofits lanch, at an altitde of two and a halfiles along with its paload of for e/pensi#eand ninsred scienti0c satellites+



1E

hen the gidance sste2s own

copter tried to con#ert one pieceof data the sidewas #elocit of therocet fro a ) bit forat to a 1bit forat4 the nber was too big,and an o#er5ow error reslted after3+6 seconds+ hen the gidance

sste shtdown, it passed controlto an identical, redndant nit, whichwas there to pro#ide bacp in caseof jst sch a failre+ 7nfortnatel,the second nit, which had failed inthe identical anner a few

illiseconds before+




11

Y2K problem:

It was sipl the ignorance abot theade8ac or otherwise of sing onl

last two digits of the ear+

.he )$digit date forat, lie 1'), wasshortened to 9$digit forat, lie )+

Some Softwarefailures



1

The Patriot Missileo :irst tie sed in ;lf war

Reasons:

A sall tiing error in the sste2s cloc

acclated to the point that after 1)hors, the tracing sste was no longeraccrate+ In the <hahran attac, the sstehad been operating for ore than 1((hors+

o 7sed as a defense fro Ira8i Scdissiles

o :ailed se#eral ties inclding one that

illed 9& 7S soldiers in <hahran, SadiArabia




1G

=art of an abort scenariofor the Shttle re8ires

fel dps to lighten thespacecraft+ It was dringthe second of thesedps that a >software?crash occrred+

+++the fel anageentodle, which hadperfored one dpand sccessfll e/ited,

restarted when recalledfor the second fel

.he Space Shttle




1H


indows @=o Microsoft released indows @= on ctober

9", 9((1+

o n the sae da copan posted 1& MB ofcopatibilit patches on the website forbg 0/es, copatibilit pdates, and

enhanceents+o .wo patches 0/ed iportant secrit holes+



18

What is softare!

• It is defined as Computer programs

an$ associated documentation



1

=rogras

perating=rocedres

<ocentation

Software=rogra<ocentationperating =rocedres

Coponents of software

What is softare!



3hat are the attri)utes of goo$ software;

.he software shold deli#er the re8ired fnctionalitand perforance to the ser and shold beaintainable, dependable and sable

• Maintainability * Software st e#ol#e to eet changing needs

• "ependability * Software st be trstworth

• #%ien%y * Software shold not ae wastefl se of sste resorces

• &sability * Software st be sable b the sers for which it was

designed



1/

<ocentation

Manals

Analsis

DSpeci0cation

<esign

Ipleentation

.esting

:oralSpeci0cationConte/t$<iagra

<ata :low<iagras

:low Charts

-ntit$Eelationship<iagra

Sorce CodeFistingsCross$EeferenceFisting .est <ata

.est Eeslts

"o%'mentation %onsists of di(erent types of

man'als are

Fist of docentation anals



12

)peratin*Pro%ed'res

&serMan'als

)perationalMan'als

+ystem

),er,ie-e*inner.s/'ide T'torial

Referen%e/'ide

Installation/'ide

+ystem

dministration/'ide

Fist of operating procedre anals+

"o%'mentation %onsists of di(erent types

of man'als are



hat is a softwareprocessG

• A set of a%ti,ities whose goal is thede#elopent or e#oltion of software

• ;eneric acti#ities in all software

processes areH * +pe%i%ation $ what the sste shold

do and its de#elopent constraints

* "e,elopment $ prodction of the

software sste * alidation $ checing that the software

is what the cstoer wants

* #,ol'tion $ changing the software inresponse to changing deands



3hat is a software process mo$el; simplied representation of a softare

pro%ess, presented fro a speci0c perspecti#e

• #3amples of pro%ess perspe%ti,es: Wor45o perspe%ti,e represents inpts, otpts and

dependencies"ata65o perspe%ti,e represents data transforation

acti#ities

Rolea%tion perspe%ti,e represents the rolesDacti#ities of thepeople in#ol#ed in software

process• /eneri% pro%ess models

* Waterfall

* #,ol'tionary de,elopment

* 8ormal transformation

* Inte*ration from re'sable %omponents



+oftare prod'%ts a be de#eloped for aparticlar cstoer or a be de#eloped for

a general aret

+oftare Prod'%t

+oftare prod'%ts a beJ/eneri% $ de#eloped to be sold to a range of diKerent cstoers

J-espo4e >csto? $ de#eloped for a single cstoer according to

their speci0cation



G

What is softare en*ineerin*!Software engineering is an engineering $iscipline which is

concerne$ with all aspects of software pro$uction

+oftare en*ineers shold

* a$opt a systematic an$ organise$ approach to their

wor%

* use appropriate tools an$ techniDues $epen$ing on

• the pro)lem to )e solve$0• the $evelopment constraints an$

• use the resources availa)le



H

At the 0rst conference on software engineering in 1'&, :ritL Baerde0ned software engineering as “.he establishent and se of sondengineering principles in order to obtain econoicall de#elopedsoftware that is reliable and wors ecientl on real achines*+

Stephen Schach de0ned the sae as “A discipline whose ai is theprodction of 8alit software, software that is deli#ered on tie, withinbdget, and that satis0es its re8ireents*+

Both the de0nitions are poplar and acceptable to ajorit+ Nowe#er,de to increase in cost of aintaining software, objecti#e is now shiftingto prodce 8alit software that is aintainable, deli#ered on tie,within bdget, and also satis0es its re8ireents+

What is softare

en*ineerin*!



8

Software Process

.he software process is the wa in which weprodce software+

h is it diclt to ipro#e softwareprocess G

Oot enogh tie

Fac of nowledge



Fearning cr#e

<o not 8it here!

Ipro#ed ftrestate=rocessipro#eent

beginsInitial

state state

=rodcti#it

.ie

rong oti#ations

Software Process

Inscient coitent



I

Software Characteristics:

Software does not wear ot+

&sef'l lifephase

Wear o'tphase

-'rn6in

phase

: a i l % r e

I n t e n s i t

.ie



/

Software is not anfactred


Eesabilit of coponents

Software is 5e/ible



2

Coparison of constrcting a bridge #is$P$#is writing a progra+

Sr"No

#onstructing a $ridge %riting a program

1.

2.

3.

4.

5.

6.

7.


.he proble is well nderstoodnl soe parts of the proble arenderstood, others are not

.here are an e/isting

bridges .he re8ireent for a bridgetpicall do not change chdring constrction .he strength and stabilit of abridge can be calclated withreasonable precisionhen a bridge collapses, there isa detailed in#estigation and

report-ngineers ha#e been constrctingbridges for thosands of ears

Materials >wood, stone,iron, steel?and techni8es >aing joints inwood, car#ing stone, casting iron?change slowl+

-#er progra is diKerent anddesigned for special applications+

Ee8ireents tpicall changedring all phases of de#elopent+Oot possible to calclate correctnessof a progra with e/isting ethods+

hen a progra fails, the reasonsare often na#ailable or e#en

deliberatel concealed+<e#elopers ha#e been writingprogras for "( ears or so+

Nardware and software changesrapidl+



GE

+ystem+ofta

re

RealTime

+oftare

#mbedded

+oftare

#n*ineerin* and

+%ienti%+oftare

Webbased

+oftarerti%ialIntelli*en

%e+oftare

Personal

9omp'ter

+oftare

-'sine

ss+oftare

Software Applications



G1

The Changing Nature ofSoftware .rend has eerged to pro#ide sorce code

to the cstoer and organiLations+

Software where sorce codes are a#ailableare nown as open sorce software+

-/aples

pen sorce softwareH FIO7@, MSQF, =N=, pen oce, Apachewebser#er etc+




G

anagement may )e confi$ent a)out goo$

stan$ar$s an$ clear proce$ures of the company.

But the taste of any food itemis in the eating;

not in the Recipe !

+oftare Myths Mana*ementPerspe%ti,es;




GG

Company has latest computers an$ stateJ

ofJtheJart software tools0 so we shoul$nKt

worry a)out the Duality of the pro$uct.

The infrastructure isonly one of the seeral factors

that determine the ualityof the product!





GH

A$$ition of more software specialists0 those with

higher s%ills an$ longer e7perience may )ring the

sche$ule )ac% on the trac%?

"nfortunately#hat may further delay the schedule!




G8

Software is eas to change

The reality is totally di$erent%

+oftare MythsMana*ement Perspe%ti,es;



G

Copters pro#ide greaterreliabilit than the de#ices thereplace

This is not always true%

+oftare MythsMana*ement Perspe%ti,es;




GI

A general statement of o)@ectives is sufficient to get

starte$ with the $evelopment of software. issing,vague

reDuirements can easily )e incorporate$,$etaile$ out as

they get concreti6e$.

&f we do so# we are headingtowards a disaster%

+oftare Myths 9'stomerPerspe%ti,es;



G/

Software with ore featres isbetter software

Software can wor right the 0rst tie

Both are only myths!

+oftare Myths 9'stomerPerspe%ti,es;




G2

Once the software is $emonstrate$0 the @o) is

$one.

"sually# the pro'lems (ust 'egin!

+oftare Myths "e,eloperPerspe%ti,es;




HE

Software Duality can not )e assesse$ )efore

testing.

weer# uality assessment techniuesshould 'e used through out thesoftware deelopment life cycle%





H1

(he only $elivera)le for a software$evelopment pro@ect is the teste$ co$e.

ted code is only one of the deliera'le!




H

Ai is to de#elop woring progras

hose days are oer% Now o'(ectie is todeelop good uality maintaina'le

programs!




HG

Some Terminologies

<eli#erables and Milestones

<iKerent deli#erables are generated dring software de#elopent+ .hee/aples are sorce code, ser anals, operating procedre anals

etc+

.he ilestones are the e#ents that are sed to ascertain the stats of theproject+ :inaliLation of speci0cation is a ilestone+ Copletion of designdocentation is another ilestone+ .he ilestones are essential for

project planning and anageent+



HH

=rodct and =rocess

Some Terminologies

=rodctH hat is deli#ered to the cstoer, is called a prodct+ It ainclde sorce code, speci0cation docent, anals, docentationetc+ Basicall, it is nothing bt a set of deli#erables onl+

=rocessH =rocess is the wa in which we prodce software+ It is thecollection of acti#ities that leads to >a part of? a prodct+ An ecientprocess is re8ired to prodce good 8alit prodcts+

If the process is wea, the end prodct will ndobtedl sKer, bt anobsessi#e o#er reliance on process is also dangeros+



H8

Some Terminologies

Measres, Metrics and Measreent

A easre pro#ides a 8antitati#e indication of the e/tent, diension,

siLe, capacit, ecienc, prodcti#it or reliabilit of soe attribtes ofa prodct or process+

Measreent is the act of e#alating a easre+

A etric is a 8antitati#e easre of the degree to which a sste,coponent or process possesses a gi#en attribte+



H

Some Terminologies

Software =rocess and =rodct Metrics

=rocess etrics 8antif the attribtes of software de#elopent processand en#ironent4

whereas prodct etrics are easres for the software prodct+

-/aples

=rocess etricsH =rodcti#it, Qalit, -cienc etc+

=rodct etricsH SiLe, Eeliabilit, Cople/it etc+



HI

=rodcti#it and -Kort

=rodcti#it is de0ned as the rate of otpt, or prodction per nit of

eKort, i+e+ the otpt achie#ed with regard to the tie taen btirrespecti#e of the cost incrred+

Nence ost appropriate nit of eKort is =erson Months >=Ms?, eaningthereb nber of persons in#ol#ed for speci0ed onths+ So, prodcti#it

a be easred as FCD=M >lines of code prodcedDperson onth?

Some Terminologies



H/

Some Terminologies

Modle and Software Coponents

.here are an de0nitions of the ter odle+ .he range fro “a

odle is a :E.EAO sbrotine* to “a odle is an Ada =acage*, to“=rocedres and fnctions of =ASCAF and C*, to “C Ra#a classes* to“Ra#a pacages* to “a odle is a wor assignent for an indi#idalde#eloper*+ All these de0nition are correct+ .he ter sbprogra is alsosed soeties in place of odle+



H2

“An independentl deli#erable piece of fnctionalit pro#iding access toits ser#ices throgh interfaces*+

“A coponent represents a odlar, deploable, and replaceable partof a sste that encapslates ipleentation and e/poses a set ofinterfaces*+

Some Terminologies



8E

Some Terminologies

;eneric and CstoiLed Software =rodcts

;eneric prodcts are de#eloped for anonos cstoers+ .he target isgenerall the entire world and an copies are e/pected to be sold+

Infrastrctre software lie operating sste, copilers, analLers, wordprocessors, CAS- tools etc+ are co#ered in this categor+

.he cstoiLed prodcts are de#eloped for particlar cstoers+ .he

speci0c prodct is designed and de#eloped as per cstoerre8ireents+ Most of the de#elopent projects >sa abot &(%?coender this categor+



8

"ependen%y

)rder

Pro<e%t Prod'%t

Pro%ess

People

1

9

3

)

Eole of Manageent in Software<e#elopent




Software &evelopment :ife Cycle

•e!uirement Analysis "

Specification

•#esign

•Coding

•$esting•%aintenance " &perations




Software :ife Cycle o$el• 3aterfall o$el

• Prototype o$el

• +terative 'nhancement o$el• 'volutionary &evelopment o$el

• Spiral o$el

• api$ Application &evelopment !A&" o$el

3 t f ll $ l




3aterfall o$el

• :inear SeDuential o$el

• Classical :ife Cycle o$elRequirement

Design

Implementationand unit testing

Integration andsystem testing

Operation &

Maintenance




Pro)lems with the 3aterfall o$el

• +t is $ifficult to $efine all reDuirements at the )eginning of

a pro@ect

•(his mo$el is not suita)le for accommo$ating anychange

• A wor%ing version of the system is not seen until late in

the pro@ectKs life

• +t $oes not scale up well to large pro@ects• eal pro@ects are rarely seDuential




Prototype o$el

• +t is also %nown as throw away mo$el.

• +t is $evelope$ as per the current availa)le

reDuirement.

• (he co$e for the prototype mo$el is

thrown awayL however the e7perience

gathere$ from $eveloping the prototype

helps in $eveloping the actual system.




8/

• :inear mo$el

• =api$>

Prototype o$el



82

Requirementsspecification

Architecturaldesign

Detailed

design

Implementationand unit testing

Integrationand testing

Operation andMaintenance

Iterati&e En'ancement !odel



E

#,ol'tionary Pro%ess Models

'volutionary process mo$el resem)les iterativeenhancement mo$el. (he same phases as $efine$ for the

waterfall mo$el occur here in a cyclical fashion. (his mo$el

$iffers from iterative enhancement mo$el in the sense that

this $oes not reDuire a usea)le pro$uct at the en$ of each

cycle. +n evolutionary $evelopment0 reDuirements are

implemente$ )y category rather than )y priority.

(his mo$el is useful for pro@ects using new technology that

is not well un$erstoo$. (his is also use$ for comple7 pro@ectswhere all functionality must )e $elivere$ at one time0 )ut the

reDuirements are unsta)le or not well un$erstoo$ at the

)eginning.




'volutionary &evelopment o$el

Validation Finalversion

Development Intermediate

versions

Specification Initial

version

Outline

description

Concurr ent

activities

Spiral o$el




Spiral o$el

Phases of Spiral o$el• 'lanningM &etermination of o)@ectives0

alternatives an$ constraints.

• is( AnalysisM Analy6e alternatives an$attempts to in$entify an$ resolve the ris%s

involve$

• #evelopmentM Pro$uct $evelopment an$testing pro$uct.

• AssessmentM Customer evaluation

Spiral o$el



G

Sp a o$e

api$ Application &evelopment !A&" o$el



H

o 4uil$ a rapi$ prototype

o Nive it to user for evaluation < o)tain fee$)ac%

o Prototype is refine$

eDuirement

sPlanning

User

&escription

Construction Cut over

3ith active participation of users

p pp p ! "



8

#ot an appropriate mo$el in the a)sence of user

participation.

eusa)le components are reDuire$ to re$uce

$evelopment time.

ighly speciali6e$ < s%ille$ $evelopers are reDuire$

an$ such $evelopers are not easily availa)le.

api$ Application &evelopment !A&" o$el

Mltiple Choice Qestions



1+1 Software isa; Sperset of progras >b? sbset ofprogras>c? Set of progras >d? none of the abo#e

1+9 hich is O. the part of operating procedre analsG>a? 7ser anals >b? perational anals

%; <ocentation anals >d? Installationanals1+3 hich is O. a software characteristicG

>a? Software does not wear ot >b? Software is5e/ible>c? Software is not anfactred d; Software isalwas correct1+) =rodct is

a; <eli#erables >b? 7ser e/pectations>c? rganiLations eKort in de#elopent >d? none ofthe abo#e

Mltiple Choice QestionsOoteH Select ost appropriate answer of the following 8estionsH

1+" .o prodce a good 8alit prodct, process shold be>a? Cople/ b; -cient>c? Eigoros >d? none of the abo#e

Mltiple Choice Qestions



I

1+ hich is not a prodct etricG

>a? SiLe >b? Eeliabilit%; =rodcti#it >d? :nctionalit

1+6 hich is O. a process etricG>a? =rodcti#it b; :nctionalit>c? Qalit >d? -cienc

1+& -Kort is easred in ters ofHa; =erson$onths >b? Epees>c? =ersons >d? Months

1+' 7MF stands for>a? 7nifor odeling langage b; 7ni0ed odeling

langage>c? 7nit odeling langage >d? 7ni#ersalodeling langage

p e C o ce Qes o sOoteH Select ost appropriate answer of the following 8estionsH

1+1( An independentl deli#erable piece of fnctionalit pro#idingaccess to

its ser#ices throgh interface is called>a? Software easreent >b? Software

coposition



(han% ou

Please forwar$ your Duery

(oM sangwan)op*aiit+amity+edu

CCM [email protected]

chap8_software engineering

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