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1. Introduction to
Software Engineering
Lecture No.04
Course Instructor: Javaria Umbreen
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2. Recap
• Process framework
• Generic process model
• The essence of practice
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3. Overview
• Process Models
▫ Perspective process models
 Waterfall
 Incremental
 Evolutionary
▫ Specialized Process Models
▫ Component-Based Development
▫ The Formal Methods Model
▫ Aspect-Oriented Software Development.
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4. • Prescriptive process models define a predefined
set of process elements and a predictable process
work flow.
• Prescriptive process models strive for structure
and order in software development.
• Activities and tasks occur sequentially with
defined guidelines for progress.
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5. The Waterfall Model
Communication
Planning
Modeling
Construction
Deployment
analysis
design
code
test
project initiation
requirement gathering estimating
scheduling
tracking
delivery
support
feedback

6. Advantages & Disadvantages
• Advantages
▫ Base model
▫ Simple and easy
▫ Small projects with well understood requirements
• Disadvantages
• No feedback
• No parallel activities
• High risk
• Need patience to see final output
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7. The V-Model

8. • Also known as verification and validation model
• Extension of waterfall model.
• Testing is associated with every phase of life
cycle
• Advantages
• Time saving
• Every component must be testable
• Progress can be tracked easily
• Proactive defect tracking
• Disadvantages
• No feedback
• Risk analysis not done
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9. The Incremental Model
C o m m u n i c a t i o n
P l a n n i n g
M o d e l i n g
C o n s t r u c t i o n
D e p l o y m e n t
d e l i v e r y
f e e d b a c k
analy sis
design code
t est
increment # 1
increment # 2
delivery of
1st increment
delivery of
2nd increment
delivery of
nt h increment
increment # n
project calendar time
C o m m u n i c a t i o n
P l a n n i n g
M o d e l i n g
C o n s t r u c t i o n
D e p l o y m e n t
d e l i v e r y
f e e d b a c k
analy sis
design code
t est
C o m m u n i c a t i o n
P l a n n i n g
M o d e l i n g
C o n s t r u c t i o n
D e p l o y m e n t
d e l i v e r y
f e e d b a c k
analysis
design
code
t es t

10. • Used when requirements are well understood
• Multiple independent deliveries are identified.
• Workflow is in a linear fashion in each
increment.
• Provides needed functionality earlier while
delivering optional components later.
• Useful when staffing is too short for full scale
development.
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11. Evolutionary Models: Prototyping
Construction
of prototype
Communicat ion
Quick plan
Const ruct ion
of
prot ot ype
Mo de ling
Quick de sign
De live ry
& Fe e dback
Deployment
communication
Quick
plan
Modeling
Quick design
Construction
of prototype
Deployment
delivery &
feedback

12. Description
• Mixture of evolutionary and iterative approach
• Used when requirements are not sure.
• Serves as mechanism to identify requirements
• Feedback is used to refine the product.
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13. Disadvantages
• Stakeholders see what appears to be a working version of
the software. They may be unaware that the prototype
architecture is also evolving. This means that the
developers may not have considered the overall software
quality or long-term maintainability.
• As a software engineer, you may be tempted to make
implementation compromises to get a prototype working
quickly. If you are not careful, these less than- ideal
choices have now become an integral part of the evolving
system.
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14. Evolutionary Models: The Spiral
communication
planning
modeling
construction
deployment
delivery
feedback
start
analysis
design
code
test
estimation
scheduling
risk analysis

15. • Objective setting: Specific objectives for the phase
are identified.
• Risk assessment and reduction: Risks are assessed
and activities are put in place to reduce the key risks.
• Development and validation: A development model
for the system is chosen which can be any of the
general models.
• Planning: The project is reviewed and the next phase
of the spiral is planned.
Spiral Model sectors

16. Spiral Model

17. • Risk handling
• Radius of spiral=cost
• Angular dimension = progress
• Meta model
• Good for large projects
• Customer satisfaction
• Disadvantages
▫ Complex
▫ Expertise
▫ Time
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18. Evolutionary Models: Concurrent
Under review
Baselined
Done
Under
revision
Await ing
changes
Under
development
none
Modeling activity
represents the state
of a software engineering
activity or task

19. Summary
• Process Models
▫ Waterfall
▫ Incremental
▫ Evolutionary
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20. Class assignment
• what happens when we emphasize development
speed over product quality?
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