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%ee of Soft&are 'ife Cycle Moels
(or More comple) systems
More chances of error prone &itho*t proper plan#cycle+
To overcome the above criteria &e nee systematic approach &hich are nothing b*t
soft&are 'ife Cycle Moels+
 
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Various Software Life Cycle Models
Soft&are life cycle moels escribe vario*s phases of the soft&are cycle an the orer
in &hich those phases are e)ec*te+ There are tons of moels- an many companies
aopt their o&n- b*t all have very similar patterns+ Some of the moels as follo&s+
 General Moel
• .ater fall moel# 'inear Se/*ential# Classic 'ife Cycle Moel 
• 1Moel
• Incremental Moel
• Spiral Moel
 
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General 'ife Cycle Moel
Soft&are life cycle moels escribe phases of the soft&are cycle an the orer in
&hich those phases are e)ec*te+ There are tons of moels- an many companies
aopt their o&n- b*t all have very similar patterns+ The general- basic moel is sho&n
belo&
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Water fall / Linear Sequential /Classic Life Cycle Model
The 9&aterfall moel9- oc*mente in !:;0 by oyce &as the first p*blicly oc*mente
life cycle moel+ The moel &as evelope to help &ith the increasing comple)ity of
aerospace pro*cts+
This is the most common an classic of life cycle moels- also referre to as a linear1
se/*ential life cycle moel+ It is very simple to *nerstan an *se+ In a &aterfall
moel- each phase m*st be complete in its entirety before the ne)t phase can begin+
 3t the en of each phase- a revie& ta<es place to etermine if the pro=ect is on the
right path an &hether or not to contin*e or iscar the pro=ect+ >nli<e &hat I
mentione in the general moel- phases o not overlap in a &aterfall moel+
The least fle)ible an most obsolete of the life cycle moels+ .ell s*ite to pro=ects
that has lo& ris< in the areas of *ser interface an performance re/*irements- b*t high
 
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Water fall model
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Water fall model (contd.)
 Simple an easy to *se+
 8asy to manage *e to the rigiity of the moel – each phase has specific
  eliverables an a revie& process+
 7hases are processe an complete one at a time+
 .or<s &ell for smaller pro=ects &here re/*irements are very &ell *nerstoo#stable+
isadvantages
 It?s iffic*lt to respon to changing c*stomer re/*irements+
 3=*sting scope *ring the life cycle can <ill a pro=ect
 %o &or<ing soft&are is pro*ce *ntil late *ring the life cycle+
 @igh amo*nts of ris< an *ncertainty+
 7oor moel for comple) an ob=ect1oriente pro=ects+
 
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V ! model
 3nother variant of the &aterfall moel the 1moel associates each evelopment
activity &ith a test or valiation at the same level of abstraction+ 8ach evelopment
activity b*ils a more etaile moel of the system than the one before it- an each
valiation tests a higher abstraction than its preecessor+
The least fle)ible an most obsolete of the life cycle moels+ .ell s*ite to pro=ects that
has lo& ris< in the areas of *ser interface an performance re/*irements- b*t high ris<
 
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V ! model (contd.)
a    t    i    o   
 g   
  g 
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V ! model (contd.)
Simple an easy to *se+
8ach phase has specific eliverables+
@igher chance of s*ccess over the &aterfall moel *e to the evelopment of test
plans early on *ring the life cycle+
.or<s &ell for small pro=ects &here re/*irements are easily *nerstoo+
isadvantages
ery rigi- li<e the &aterfall moel+
'ittle fle)ibility an a=*sting scope is iffic*lt an e)pensive+
Soft&are is evelope *ring the implementation phase- so no early prototypes of the
soft&are are pro*ce+
 
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"ncremental/"terative model
  This moel oes not attempt to start &ith f*ll specification of re/*irements+ M*ltiple
evelopment cycles ta<e place here- ma<ing the life cycle a m*lti1&aterfallD cycle+
Cycles are ivie *p into smaller- more easily manage iterations+ 8ach iteration
passes thro*gh the re/*irements- esign- implementation an testing phases+
  3 &or<ing version of soft&are is pro*ce *ring the first iteration- so yo* have &or<ing
soft&are early on *ring the soft&are life cycle+ S*bse/*ent iterations b*il on the
initial soft&are pro*ce *ring the first iteration+
Eey 7oints
4evelopment an elivery is bro<en o&n into increments
8ach increment elivers part of the re/*ire f*nctionality
e/*irements are prioritise an the highest priority re/*irements are incl*e in early
increments
Fnce the evelopment of an increment is starte- the re/*irements are froen
 
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"ncremental/"terative model (contd.)
Analysis   System Design
Increment
  o    f    i  n   c   r  e   m   e   n
   t  s
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"ncremental/"terative model (contd.)
Advantages
System f*nctionality is available earlier an c*stomer oes not have to &ait as long+
8arly increments act as a prototype to help elicit re/*irements for later increments+
The highest priority f*nctionalities ten to receive more testing+
More fle)ible – less costly to change scope an re/*irements+
8asier to test an eb*g *ring a smaller iteration+
8asier to manage ris< beca*se ris<y pieces are ientifie an hanle *ring its
iteration+
isadvantages
8ach phase of an iteration is rigi an o not overlap each other+
7roblems may arise pertaining to system architect*re beca*se not all re/*irements are
 
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#rototy$e model
In this moel- a prototype 5an early appro)imation of a final system or pro*ct is b*ilt-
teste- an then re&or<e as necessary *ntil an acceptable prototype is finally achieve
from &hich the complete system or pro*ct can no& be evelope+
  7rototype paraigm begins &ith re/*irements gathering+ 4eveloper an c*stomer meet
an efine the overall ob=ectives for the soft&are- ientify &hatever re/*irements are
<no&n- an o*tline areas &here f*rther efinition is manatory+
  3 /*ic< esign occ*rs &hich leas to the constr*ction of prototype+
  The prototype is eval*ate by the c*stomer#*ser an *se to refine the re/*irements for
the soft&are to be evelope+
  Iteration occ*rs as the prototype is t*ne to satisfy the *ser re/*irements- &hile at the
 
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#rototy$e model
>nerstaning the re/*irements for the *ser interface
8)amining feasibility of a propose esign approach
4isavantages
Listen to
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S$iral ! model 7resente by Boehm in !:A$+ The spiral moel is foc*se on ris< management+
This moel of evelopment combines the feat*res of the prototyping moel an the
&aterfall moel+ The spiral moel is favore for large- e)pensive- an complicate
pro=ects+
The spiral moel is similar to the incremental moel- &ith more emphases place on ris<
analysis+ The spiral moel has fo*r phasesH 7lanning- is< 3nalysis- 8ngineering an
8val*ation+ 3 soft&are pro=ect repeately passes thro*gh these phases in iterations
5calle Spirals in this moel+ The baseline spiral- starting in the planning phase-
re/*irements is gathere an ris< is assesse+ 8ach s*bse/*ent spiral b*ils on the
baseline spiral+
e/*irements are gathere *ring the planning phase+ In the ris< analysis phase- a
process is *nerta<en to ientify ris< an alternate sol*tions+ 3 prototype is pro*ce at
the en of the ris< analysis phase+
Soft&are is pro*ce in the engineering phase- along &ith testing at the en of the
phase+ The eval*ation phase allo&s the c*stomer to eval*ate the o*tp*t of the pro=ect to
ate before the pro=ect contin*es to the ne)t spiral+
In the spiral moel- the ang*lar component represents progress- an the rai*s of the
spiral represents cost+
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Spiral – moel 5cont+
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S$iral % model (contd.)
@igh amo*nt of ris< analysis+
is<s are e)plicitly assesse an resolve thro*gho*t the process
(oc*s on early error etection an esign fla&s+
Goo for large an mission1critical pro=ects+
Soft&are is pro*ce early in the soft&are life cycle+
isadvantages
is< analysis re/*ires highly specific e)pertise+
7ro=ect?s s*ccess is highly epenent on the ris< analysis phase+
4oesn?t &or< &ell for smaller pro=ects+
 
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&a$id A$$lication evelo$ment (&A) model
34 moel ma<es heavy *se of re*sable soft&are components &ith an e)tremely short
evelopment cycle+
  The 34 is a linear se/*ential soft&are evelopment process that emphasies an
e)tremely short evelopment cycle+ The 34 soft&are moel is a 9high spee9
aaptation of the linear se/*ential moel in &hich rapi evelopment is achieve by
*sing a component1base constr*ction approach+ >se primarily for information systems
applications- the 34 approach encompasses the follo&ing phases
B*siness moeling
Testing
  34 process emphasies re*se many of the program components have alreay been
teste- &hich minimies the testing an evelopment time+
 
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'ourt eneration (*+) +ecniques
  Soft&are tool is *se to generate the so*rce coe a*tomatically for a soft&are
 
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