MODULE-
I
Int
roduct i
on:Softwar eCri
sis,NeedforSoftwareEngineer
ing.ProfessionalSoft
wareDev el
opment,
SoftwareEngineer i
ngEt hi
cs.CaseStudies.
Softwar eProcesses:Model s:Waterfal
lModel(Sec2.1.
1),I
ncrement alModel(Sec2. 1.2)andSpir
al
Model (Sec2.1.3).Processactiv
iti
es.
Requirement s Engi neeri
ng: Requirements Engineer
ing Processes ( Chap 4) . Requirements
Eli
cit
ationand Anal y si
s( Sec4.5).Functi
onaland non-functi
onalr equirements( Sec4. 1)
.The
soft
war eRequi r
ement sDocument( Sec4.2).Requir
ementsSpecificati
on( Sec4.3).Requirements
val
idati
on( Sec4.6).RequirementsManagement( Sec4.
7).
I
ntr
oducti
on
Sof
twareCri
sis
Themostv isibl
esy mpt omsoft hesof twar ecrisi sar e
Latedel i
v ery,ov erbudget
Pr oductdoesnotmeetspeci fiedr equi rement s
Inadequat edocument ation
Softwar edel iverywhi chsomeki ndofer r
or soraf terthecompl et
ionoft heschedul eddat e
causeshugef manci allossesandi sal soext r
emel yinconv eni entonone' spar tashi story
tell
sus.Si t
uat ionsliket heY2Kpr obl em whi chwasdi sast r
ousi nmostoft hecount r
iesi s
consider edt obeoneoft hecat ast rophicf ai l
ur esi ntermsofeconomi c,admi nistrativeand
polit
icalf unct ioningmaybet ermedasaSof twar eCr i
sis.ThusaSof twar ecr isi
smaybe
explainedasami smat chinsof twar edel iver ablesandt heexpect ati
onsauserhav efr om t he
comput ersy stem int ermsofi tscapaci tyt owor k.Dur ing20t hcent uryitwasanemer gi
ng
issuesi ncecomput i
ngf l
our ishedandsof twar ewasi ncapabl et ocat chup.Duet ot he
softwar ecr isis,programmer shadt ost r
uggl eal way sinor dert okeeppace.
The2003Nor t
heastbl ackoutwasoneoft hemosti mpor tantpowersy stem f ai
lur esi n
theNor thAmer icanhi story .Duet ot hisbl ackout ,largenumberofpowerpl ant sf ail
ed
andappr oximat elyfi
ftymi llioncust omer sf acedpowerl osswhi chresul tedi nahuge
fmanci al t
hreatt ocurrency .Af t
er war ds, itwasunder stoodt hatasof twar ebugwas
ther easonbehi ndt hisunpr ecedent edf ailur
ei nthepowermoni t
oring/ notingal ong
wi ththemanagementsy stem.
Y2Kpr obl em basi call
yref erredt ot hehugeamountofdr awbacki nt hepr ocessi ngof
dat aaf terthey ear2000.Dur i
ng1990s, realizati
onoft heexper tsbegant ounder stand
thisimpor tantshor tcomi ngi ncomput erappl i
cationandt heninor dert ohandl esuch
apr obl em mi l
lionswer espent .
They ear1996phy si
call
ywi t
nessedtheendofAr ian- 5spacer ocketwhi chwasmade
withacostof$7000mi l
li
onwi t
hinaper i
odoft eny earsinlesst hanami nuteafterthe
rocketlaunch.Itwasl at
erobservedthattherewasasof twar ebugi nther ocket
guidancesy stem.
Oneoft hebiggestbanksofUSi n1996, didwrongcal culati
onoft hecreditedaccount s
ofappr oxi
mat el
y800cust omerst ot
heamountof$9241acs.I twasl aterdetected
thattheproblem tookplaceduet oapr ogrammi ngbugi nthebanki ngsof t
war e.
Att hetimeoftheGul fWarin1991, theU.S.A.Pat ri
otmi ssilesactedasadef ence
againstScudmi ssi
lesusedbyI r
aq.Butt hePatriotfai
ledtot argethittheScudsev eral
ti
mes.Thus, t
went yei
ghtUSsol di
erswer eputt osleepinDhahr an,Saudi Arabia.An
inquiry
, i
ntotheinci
dentmadecleart
hecauseofthefai
l
edtargetast
hesmal
lbugagai
nand
f
inal
l
yr esul
tedi
nthewrongcalcul
ati
onofthemissi
l
epath.
Needf orSoftwareEngineer i
ng
Theneedofsof twareengineeri
ngar i
sesbecauseofhi gherrateofchangei nuserr equir
ements
andenvironmentonwhi cht hesoftwareisworking.
Largesof t
ware-Itiseasiertobuil
dawal lthant oahouseorbui l
di ng,li
kewise,asthesizeof
softwarebecomel argeengineeri
nghast osteptogiveitascient ifi
cprocess.
Scalabil
it
y-Ifthesoftwareprocesseswerenotbasedonsci ent
ificandengi neeringconcepts,
i
twoul dbeeasiertor e-
creat
enewsof twaret hant
oscaleanexi stingone.
Cost -Ashardwareindustryhasshowni t
sski l
lsandhugemanuf act uri
nghasl owerdownt he
pri
ceofcomput erandel ectr
onichardware.Butthecostofsof twar eremainshi ghifpr
oper
processisnotadapt ed.
Dynami cNatur
e-Thealwaysgrowingandadaptingnat
ureofsof
twarehugelydependsuponthe
envi
ronmentinwhichuserworks.I
fthenatur
eofsoftwar
eisalwayschanging,new
enhancementsneedtobedonei ntheexi
sti
ngone.Thisi
swheresoftwareengineer
ingpl
ays
agoodr ol
e.
Qualit
yManagement -Bet
terpr
ocessofsoftwaredevel
opmentprovi
desbetterandquali
ty
sof
twareproduct
.
Pr
ofessi
onalSof
twar
eDevel
opment
Whati
ssoftwar e?
Sof t
war eisasetofapr ogram associ atedwi thdocument ati
onandconf i
gurati
ondat at hatis
neededt omaket hesepr ogramsoper atecor rectly.
Asof twar esy st em usual l
yconsi sts:ofanumberofsepar atepr ograms,conf igurationfil
es,
whichar eused t o setup t hesepr ograms,sy stem document ation,whi chdescr ibesthe
str
uctur eoft hesy stem,anduserdocument ation,whi chexpl ainshowt ouset hesy stem and
websi tesoruser st odownl oadr ecentpr oducti nformat ion.
Softwar eproduct smaybe
o Gener i
c-dev elopedt obesol dtoar angeofdi fferentcust omer s
o Bespoke( cust om)dev elopedf orasi nglecust omeraccor di
ngt ot hei
rspecifi
cat ion
Whati
ssoftwar eengi neer ing?
Sof twar eengi neer ingi sanengi neeringdi sciplinewhi chi sconcer nedwi thallaspect sof
softwar epr oduct ion.
Engi neer ingdi scipli
ne
Engi neer smaket hingswor k.Theyappl yt heories,met hodsandt oolswher et heseare
appr opriate,butt heyuset hem sel ectivelyandal wayst ryt odi scoversol utionsto
pr oblemsev enwhent herear enoappl icablet heoriesandmet hods.
Engi neer salsor ecogni sethatt heymustwor ktoor ganisat i
onal andf i
nancial
const raints,sot heylookf orsol utionswi thi
nt heseconst rai
nts.
Al laspect sofsof twar epr oduct i
on
Sof
twareengineer
ingi snotjustconcernedwi
tht hetechni
calprocessesofsof
tware
dev
elopmentbutalsowi t
hact i
vi
ti
essuchassoft
war eproj
ectmanagementandwiththe
dev
elopmentoftools,
met hodsandtheor
iest
osupportsoft
warepr
oduction.
,Whatisthedi
ffer
encebetweensoftwareengineeri
ngandcomput erscience?
Computersci
enceisconcer
nedwiththeoryandfundamentals;
soft
wareengi neer
ingisconcer
ned
wit
hthepract
ical
i
tiesofdevel
opi
nganddel i
veri
ngusefulsof
tware.
Computersci
encetheori
esarecur
rentl
yinsuf
fici
enttoactasacompleteunder pi
nningforsof
twar
e
engi
neeri
ng
Whatisthedi
ffer
encebetweensoftwareengineeri
ngandsy st
em engineeri
ng?
Sy stem engi neeri
ngisconcernedwi thallaspect
sofcomput er-basedsy stems
developmenti ncludi
nghardwar e,soft
war eandprocessengi neer i
ng.
Sy stem engi neersarei
nvol
vedi nsy st
em specifi
cat
ion,architecturaldesign,i
ntegrat
ionand
deployment .
Sof twareengi neeri
ngispartoft hi
spr ocessconcer
nedwi thdev el
opingthesof tware
inf
rastructure,contr
ol,
appli
cati
onsanddat abasesinthesy stem.
Whatisasof twar eprocess?
Asoft
war eprocessi sthesetofactivi
tiesandassoci at
edresult
st hatpr oduceasof twarepr .4
oduct
Gener
icactivi
tiesinallsoft
wareprocessesar e:
Speci
fi
cat
ion-whatt
hesy
stem shoul
ddoandi
tsdev
elopmentconst
rai
nts.
Dev
elopment-producti
onoft
hesoft
waresy
stem.
Val
i
dation-checki
ngthatt
hesof
twarei
swhatthecust
omerwant
s.
Evol
uti
on-changingt
hesoft
war
einresponset
ochangi
ngdemands.
Whatisasoftwareprocessmodel?
Asimpli
fi
edrepresent
ati
onofasoftwar
epr
ocess,pr
esent
edf
rom aspeci
fi
cper
spect
ive4Exampl
es
ofpr
ocessperspecti
vesare
Awor kl owmodel -sequenceofact i
vities
Adat a-fl
owmodel -informat ionf low
Ar ole/actionmodel -whodoeswhat
Gener
icprocessmodel s
Thewat er
fallappr oach: separ atepr ocessphasessuchasr equir
ementsspeci fi
cation,
sof twaredesi gn, i
mpl ement ation,test i
ngandsoon.Af tereachst ageisdef i
nediti s
'
signed- off,
anddev elopmentgoesont ot hef oll
owingst age.
Iterat i
v edevelopment :
Thi sappr oachi nterleav estheact i
viti
esofspecifi
cation,
dev elopmentandv al
idation.
Component -
basedsof twareengi neering( CBSE) :
Thist echni queassumest hatpar tsof
thesy st
em al r
eadyexi st.Thesy st
em dev elopmentpr ocessf ocusesonint egrati
ng
thesepar t
sr athert handev elopingt hem f rom scratch.
Whatarethecost sofsof twar eengi neering?
Roughl y60%ofcost saredev elopmentcost s,40%ar etestingcost s.Forcustom sof tware,
ev olutioncost sof tenexceeddev elopmentcost s.
Cost sv arydependi ngont het ypeofsy stem bei ngdev el
opedandt herequir
ement sof
sy stem at tr
ibutessuchasper formanceandsy stem reli
abili
ty .
Distribut i
onofcost sdependsont hedev elopmentmodel t
hati sused.
, Whataret heat tr
ibutesofgoodsof tware?
Thesof t wareshoul ddelivertherequiredfunctional
it
yandper f
ormancet ot heuserand
shouldbemai ntainabl
e, dependableandaccept abl
e.
Mai nt
ai nabil
it
y :Softwaremustev olvetomeetchangi ngneeds;
Dependabi l
ity
:Sof twaremustbet r
ustworthy;(i
thasar angeofcharacterist
ic,
incl
udi
ng
rel
iabil
ity,secur i
tyandsaf ety).
Ef fi
ciency :Softwar eshoul dnotmakewast efuluseofsy st
em resources;
Accept abili
ty/
Usabi li
ty:
Sof twaremustaccept edbytheusersforwhi chitwasdesigned.Thi
s
meansi tmustbeunder standable,usableandcompat i
blewit
hot hersystems.
Whataret hekeychal lengesfacingsof tware
engineering
Het
erogenei
ty:Devel
opingtechni
quesforbui
l
dingsoftwaret
hatcancopewi
th
heter
ogeneousplatfor
msandexecutionenvir
onments;
Del
i
very:Dev
elopingtechni
questhatl
eadtofasterdel
i
v er
yofsof
tware;
Trust
:Devel
opi
ngt
echni
quest
hatdemonst
rat
ethatsof
twar
ecanbe
t
rust
edbyit
susers.
I
Int
roduct i
on:Softwar eCri
sis,NeedforSoftwareEngineer
ing.ProfessionalSoft
wareDev el
opment,
SoftwareEngineer i
ngEt hi
cs.CaseStudies.
Softwar eProcesses:Model s:Waterfal
lModel(Sec2.1.
1),I
ncrement alModel(Sec2. 1.2)andSpir
al
Model (Sec2.1.3).Processactiv
iti
es.
Requirement s Engi neeri
ng: Requirements Engineer
ing Processes ( Chap 4) . Requirements
Eli
cit
ationand Anal y si
s( Sec4.5).Functi
onaland non-functi
onalr equirements( Sec4. 1)
.The
soft
war eRequi r
ement sDocument( Sec4.2).Requir
ementsSpecificati
on( Sec4.3).Requirements
val
idati
on( Sec4.6).RequirementsManagement( Sec4.
7).
I
ntr
oducti
on
Sof
twareCri
sis
Themostv isibl
esy mpt omsoft hesof twar ecrisi sar e
Latedel i
v ery,ov erbudget
Pr oductdoesnotmeetspeci fiedr equi rement s
Inadequat edocument ation
Softwar edel iverywhi chsomeki ndofer r
or soraf terthecompl et
ionoft heschedul eddat e
causeshugef manci allossesandi sal soext r
emel yinconv eni entonone' spar tashi story
tell
sus.Si t
uat ionsliket heY2Kpr obl em whi chwasdi sast r
ousi nmostoft hecount r
iesi s
consider edt obeoneoft hecat ast rophicf ai l
ur esi ntermsofeconomi c,admi nistrativeand
polit
icalf unct ioningmaybet ermedasaSof twar eCr i
sis.ThusaSof twar ecr isi
smaybe
explainedasami smat chinsof twar edel iver ablesandt heexpect ati
onsauserhav efr om t he
comput ersy stem int ermsofi tscapaci tyt owor k.Dur ing20t hcent uryitwasanemer gi
ng
issuesi ncecomput i
ngf l
our ishedandsof twar ewasi ncapabl et ocat chup.Duet ot he
softwar ecr isis,programmer shadt ost r
uggl eal way sinor dert okeeppace.
The2003Nor t
heastbl ackoutwasoneoft hemosti mpor tantpowersy stem f ai
lur esi n
theNor thAmer icanhi story .Duet ot hisbl ackout ,largenumberofpowerpl ant sf ail
ed
andappr oximat elyfi
ftymi llioncust omer sf acedpowerl osswhi chresul tedi nahuge
fmanci al t
hreatt ocurrency .Af t
er war ds, itwasunder stoodt hatasof twar ebugwas
ther easonbehi ndt hisunpr ecedent edf ailur
ei nthepowermoni t
oring/ notingal ong
wi ththemanagementsy stem.
Y2Kpr obl em basi call
yref erredt ot hehugeamountofdr awbacki nt hepr ocessi ngof
dat aaf terthey ear2000.Dur i
ng1990s, realizati
onoft heexper tsbegant ounder stand
thisimpor tantshor tcomi ngi ncomput erappl i
cationandt heninor dert ohandl esuch
apr obl em mi l
lionswer espent .
They ear1996phy si
call
ywi t
nessedtheendofAr ian- 5spacer ocketwhi chwasmade
withacostof$7000mi l
li
onwi t
hinaper i
odoft eny earsinlesst hanami nuteafterthe
rocketlaunch.Itwasl at
erobservedthattherewasasof twar ebugi nther ocket
guidancesy stem.
Oneoft hebiggestbanksofUSi n1996, didwrongcal culati
onoft hecreditedaccount s
ofappr oxi
mat el
y800cust omerst ot
heamountof$9241acs.I twasl aterdetected
thattheproblem tookplaceduet oapr ogrammi ngbugi nthebanki ngsof t
war e.
Att hetimeoftheGul fWarin1991, theU.S.A.Pat ri
otmi ssilesactedasadef ence
againstScudmi ssi
lesusedbyI r
aq.Butt hePatriotfai
ledtot argethittheScudsev eral
ti
mes.Thus, t
went yei
ghtUSsol di
erswer eputt osleepinDhahr an,Saudi Arabia.An
inquiry
, i
ntotheinci
dentmadecleart
hecauseofthefai
l
edtargetast
hesmal
lbugagai
nand
f
inal
l
yr esul
tedi
nthewrongcalcul
ati
onofthemissi
l
epath.
Needf orSoftwareEngineer i
ng
Theneedofsof twareengineeri
ngar i
sesbecauseofhi gherrateofchangei nuserr equir
ements
andenvironmentonwhi cht hesoftwareisworking.
Largesof t
ware-Itiseasiertobuil
dawal lthant oahouseorbui l
di ng,li
kewise,asthesizeof
softwarebecomel argeengineeri
nghast osteptogiveitascient ifi
cprocess.
Scalabil
it
y-Ifthesoftwareprocesseswerenotbasedonsci ent
ificandengi neeringconcepts,
i
twoul dbeeasiertor e-
creat
enewsof twaret hant
oscaleanexi stingone.
Cost -Ashardwareindustryhasshowni t
sski l
lsandhugemanuf act uri
nghasl owerdownt he
pri
ceofcomput erandel ectr
onichardware.Butthecostofsof twar eremainshi ghifpr
oper
processisnotadapt ed.
Dynami cNatur
e-Thealwaysgrowingandadaptingnat
ureofsof
twarehugelydependsuponthe
envi
ronmentinwhichuserworks.I
fthenatur
eofsoftwar
eisalwayschanging,new
enhancementsneedtobedonei ntheexi
sti
ngone.Thisi
swheresoftwareengineer
ingpl
ays
agoodr ol
e.
Qualit
yManagement -Bet
terpr
ocessofsoftwaredevel
opmentprovi
desbetterandquali
ty
sof
twareproduct
.
Pr
ofessi
onalSof
twar
eDevel
opment
Whati
ssoftwar e?
Sof t
war eisasetofapr ogram associ atedwi thdocument ati
onandconf i
gurati
ondat at hatis
neededt omaket hesepr ogramsoper atecor rectly.
Asof twar esy st em usual l
yconsi sts:ofanumberofsepar atepr ograms,conf igurationfil
es,
whichar eused t o setup t hesepr ograms,sy stem document ation,whi chdescr ibesthe
str
uctur eoft hesy stem,anduserdocument ation,whi chexpl ainshowt ouset hesy stem and
websi tesoruser st odownl oadr ecentpr oducti nformat ion.
Softwar eproduct smaybe
o Gener i
c-dev elopedt obesol dtoar angeofdi fferentcust omer s
o Bespoke( cust om)dev elopedf orasi nglecust omeraccor di
ngt ot hei
rspecifi
cat ion
Whati
ssoftwar eengi neer ing?
Sof twar eengi neer ingi sanengi neeringdi sciplinewhi chi sconcer nedwi thallaspect sof
softwar epr oduct ion.
Engi neer ingdi scipli
ne
Engi neer smaket hingswor k.Theyappl yt heories,met hodsandt oolswher et heseare
appr opriate,butt heyuset hem sel ectivelyandal wayst ryt odi scoversol utionsto
pr oblemsev enwhent herear enoappl icablet heoriesandmet hods.
Engi neer salsor ecogni sethatt heymustwor ktoor ganisat i
onal andf i
nancial
const raints,sot heylookf orsol utionswi thi
nt heseconst rai
nts.
Al laspect sofsof twar epr oduct i
on
Sof
twareengineer
ingi snotjustconcernedwi
tht hetechni
calprocessesofsof
tware
dev
elopmentbutalsowi t
hact i
vi
ti
essuchassoft
war eproj
ectmanagementandwiththe
dev
elopmentoftools,
met hodsandtheor
iest
osupportsoft
warepr
oduction.
,Whatisthedi
ffer
encebetweensoftwareengineeri
ngandcomput erscience?
Computersci
enceisconcer
nedwiththeoryandfundamentals;
soft
wareengi neer
ingisconcer
ned
wit
hthepract
ical
i
tiesofdevel
opi
nganddel i
veri
ngusefulsof
tware.
Computersci
encetheori
esarecur
rentl
yinsuf
fici
enttoactasacompleteunder pi
nningforsof
twar
e
engi
neeri
ng
Whatisthedi
ffer
encebetweensoftwareengineeri
ngandsy st
em engineeri
ng?
Sy stem engi neeri
ngisconcernedwi thallaspect
sofcomput er-basedsy stems
developmenti ncludi
nghardwar e,soft
war eandprocessengi neer i
ng.
Sy stem engi neersarei
nvol
vedi nsy st
em specifi
cat
ion,architecturaldesign,i
ntegrat
ionand
deployment .
Sof twareengi neeri
ngispartoft hi
spr ocessconcer
nedwi thdev el
opingthesof tware
inf
rastructure,contr
ol,
appli
cati
onsanddat abasesinthesy stem.
Whatisasof twar eprocess?
Asoft
war eprocessi sthesetofactivi
tiesandassoci at
edresult
st hatpr oduceasof twarepr .4
oduct
Gener
icactivi
tiesinallsoft
wareprocessesar e:
Speci
fi
cat
ion-whatt
hesy
stem shoul
ddoandi
tsdev
elopmentconst
rai
nts.
Dev
elopment-producti
onoft
hesoft
waresy
stem.
Val
i
dation-checki
ngthatt
hesof
twarei
swhatthecust
omerwant
s.
Evol
uti
on-changingt
hesoft
war
einresponset
ochangi
ngdemands.
Whatisasoftwareprocessmodel?
Asimpli
fi
edrepresent
ati
onofasoftwar
epr
ocess,pr
esent
edf
rom aspeci
fi
cper
spect
ive4Exampl
es
ofpr
ocessperspecti
vesare
Awor kl owmodel -sequenceofact i
vities
Adat a-fl
owmodel -informat ionf low
Ar ole/actionmodel -whodoeswhat
Gener
icprocessmodel s
Thewat er
fallappr oach: separ atepr ocessphasessuchasr equir
ementsspeci fi
cation,
sof twaredesi gn, i
mpl ement ation,test i
ngandsoon.Af tereachst ageisdef i
nediti s
'
signed- off,
anddev elopmentgoesont ot hef oll
owingst age.
Iterat i
v edevelopment :
Thi sappr oachi nterleav estheact i
viti
esofspecifi
cation,
dev elopmentandv al
idation.
Component -
basedsof twareengi neering( CBSE) :
Thist echni queassumest hatpar tsof
thesy st
em al r
eadyexi st.Thesy st
em dev elopmentpr ocessf ocusesonint egrati
ng
thesepar t
sr athert handev elopingt hem f rom scratch.
Whatarethecost sofsof twar eengi neering?
Roughl y60%ofcost saredev elopmentcost s,40%ar etestingcost s.Forcustom sof tware,
ev olutioncost sof tenexceeddev elopmentcost s.
Cost sv arydependi ngont het ypeofsy stem bei ngdev el
opedandt herequir
ement sof
sy stem at tr
ibutessuchasper formanceandsy stem reli
abili
ty .
Distribut i
onofcost sdependsont hedev elopmentmodel t
hati sused.
, Whataret heat tr
ibutesofgoodsof tware?
Thesof t wareshoul ddelivertherequiredfunctional
it
yandper f
ormancet ot heuserand
shouldbemai ntainabl
e, dependableandaccept abl
e.
Mai nt
ai nabil
it
y :Softwaremustev olvetomeetchangi ngneeds;
Dependabi l
ity
:Sof twaremustbet r
ustworthy;(i
thasar angeofcharacterist
ic,
incl
udi
ng
rel
iabil
ity,secur i
tyandsaf ety).
Ef fi
ciency :Softwar eshoul dnotmakewast efuluseofsy st
em resources;
Accept abili
ty/
Usabi li
ty:
Sof twaremustaccept edbytheusersforwhi chitwasdesigned.Thi
s
meansi tmustbeunder standable,usableandcompat i
blewit
hot hersystems.
Whataret hekeychal lengesfacingsof tware
engineering
Het
erogenei
ty:Devel
opingtechni
quesforbui
l
dingsoftwaret
hatcancopewi
th
heter
ogeneousplatfor
msandexecutionenvir
onments;
Del
i
very:Dev
elopingtechni
questhatl
eadtofasterdel
i
v er
yofsof
tware;
Trust
:Devel
opi
ngt
echni
quest
hatdemonst
rat
ethatsof
twar
ecanbe
t
rust
edbyit
susers.
