The document contains slides from a lecture on software engineering process models. It discusses the waterfall model, V-model, incremental model and evolutionary models. The waterfall model follows sequential phases from requirements to maintenance without overlap. The V-model pairs each development phase with a testing phase. The incremental model combines linear and parallel activities to deliver software in increments. Evolutionary models take an iterative approach where software evolves over time through incremental improvements.

1. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009). Slides copyright 2009 by Roger Pressman. 1
Chapter 2
 Process Models
Slide Set to accompany
Software Engineering: A Practitioner’s Approach, 7/e
by Roger S. Pressman
Slides copyright © 1996, 2001, 2005, 2009 by Roger S. Pressman
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2. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009). Slides copyright 2009 by Roger Pressman. 2
A Generic Process Model

3. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009). Slides copyright 2009 by Roger Pressman. 3
Process Flow

4. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009). Slides copyright 2009 by Roger Pressman. 4
Identifying a Task Set
 A task set defines the actual work to be done to
accomplish the objectives of a software
engineering action.
 A list of the task to be accomplished
 A list of the work products to be produced
 A list of the quality assurance filters to be applied

5.  Activity. (communication )
 Action (“requirements gathering”)
 Goal (requirements gathering is to understand what various stakeholders want
from the software that is to be built.)
 For a small, relatively simple project, the task set for requirements gathering
might look like this:
 1. Make a list of stakeholders for the project.
 2. Invite all stakeholders to an informal meeting.
 3. Ask each stakeholder to make a list of features and functions required.
 4. Discuss requirements and build a final list.
 5. Prioritize requirements.
 6. Note areas of uncertainty.
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill 2009). Slides copyright 2009 by Roger Pressman. 5

6. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009). Slides copyright 2009 by Roger Pressman. 6
Process Assessment and Improvement
 Standard CMMI Assessment Method for Process Improvement
(SCAMPI) — provides a five step process assessment model that
incorporates five phases: initiating, diagnosing, establishing, acting and
learning.
 CMM-Based Appraisal for Internal Process Improvement (CBA
IPI)—provides a diagnostic technique for assessing the relative
maturity of a software organization; uses the SEI CMM as the basis for
the assessment [Dun01]
 SPICE—The SPICE (ISO/IEC15504) standard defines a set of
requirements for software process assessment. The intent of the
standard is to assist organizations in developing an objective
evaluation of the efficacy of any defined software process. [ISO08]
 ISO 9001:2000 for Software—a generic standard that applies to any
organization that wants to improve the overall quality of the products,
systems, or services that it provides. Therefore, the standard is directly
applicable to software organizations and companies. [Ant06]

7. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009). Slides copyright 2009 by Roger Pressman. 7
Prescriptive Models
strive for structure and order
 Prescriptive process models advocate an orderly
approach to software engineering
That leads to a few questions …
 If prescriptive process models strive for structure and
order, are they inappropriate for a software world that
thrives on change?
 Yet, if we reject traditional process models (and the
order they imply) and replace them with something less
structured, do we make it impossible to achieve
coordination and coherence in software work?

8. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009). Slides copyright 2009 by Roger Pressman. 8
The Waterfall Model
classic life cycle, suggests a systematic,sequential approach
Communication
Planning
Modeling
Construction
Deployment
analysis
design
code
test
project init iat ion
requirement gat hering estimating
scheduling
tracking
delivery
support
f eedback
 when well-defined adaptations or enhancements to an existing
system must be made (e.g., an adaptation to accounting software that
has been mandated because of changes to government regulations).
 healthcare, control system for nuclear facilities, space shuttles etc

9. Advantages of waterfall
model
 This model is simple and easy to understand
and use.
 It is easy to manage due to the rigidity of the
model – each phase has specific deliverables
and a review process.
 In this model phases are processed and
completed one at a time. Phases do not
overlap.
 Waterfall model works well for smaller projects
where requirements are clearly defined and
very well understood.
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(McGraw-Hill 2009). Slides copyright 2009 by Roger Pressman. 9

10. Disadvantages of waterfall
model
 Once an application is in the testing stage, it is very
difficult to go back and change something that was not
well-thought out in the concept stage.
 No working software is produced until late during the life
cycle.
 High amounts of risk and uncertainty.
 Not a good model for complex and object-oriented
projects.
 Poor model for long and ongoing projects.
 Not suitable for the projects where requirements are at a
moderate to high risk of changing.
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11. When to use Waterfall
Model
 This model is used only when the requirements
are very well known, clear and fixed.
 Product definition is stable.
 Technology is understood.
 There are no ambiguous requirements
 Ample resources with required expertise are
available freely
 The project is short.
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill 2009). Slides copyright 2009 by Roger Pressman. 11

12. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009). Slides copyright 2009 by Roger Pressman. 12
The V-Model (Verification and
Validation model.)

13. The V-Model
 The V-Model is an extension of the waterfall
model and is based on the association of a
testing phase for each corresponding
development stage. This means that for every
single phase in the development cycle, there is
a directly associated testing phase. This is a
highly-disciplined model and the next phase
starts only after completion of the previous
phase.
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(McGraw-Hill 2009). Slides copyright 2009 by Roger Pressman. 13

14. The Incremental Model
 initial software requirements are reasonably
well defined
 but the overall scope of the development effort
precludes a purely linear process
 compelling need to provide a limited set of
software functionality to users quickly
 The incremental model combines elements of
linear and parallel process flows
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill 2009). Slides copyright 2009 by Roger Pressman. 14

15. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
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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
analysis
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
analysis
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 est

16. The Incremental Model
 For example, word-processing software
 When an incremental model is used, the first
increment is often a core product.
 That is, basic requirements are addressed but
many supplementary features (some known,
others unknown) remain undelivered.
 The core product is used by the customer
 (or undergoes detailed evaluation).
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill 2009). Slides copyright 2009 by Roger Pressman. 16

17. The Incremental Model
 Incremental development is particularly useful
when staffing is unavailable for a complete
implementation by the business deadline that
has been established for the project.
 In addition, increments can be planned to
manage technical risks.
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill 2009). Slides copyright 2009 by Roger Pressman. 17

18. Evolutionary Models
 Software, like all complex systems, evolves over a
period of time.
 Evolutionary models are iterative.
 Factors:
 Business and product requirements often change as development
proceeds, making a straight line path to an end product unrealistic;
 tight market deadlines; a limited version
 a set of core product or system requirements is well understood
They are characterized in a manner that enables you to develop
increasingly more complete versions of the software
18

19. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009). Slides copyright 2009 by Roger Pressman. 19
Evolutionary Models: Prototyping
Construction
of prototype
Communicat ion
Quick plan
Const ruct ion
of
prot ot ype
Mode ling
Quick de sign
De live ry
& Fe e dback
Deployment
communication
Quick
plan
Modeling
Quick design
Construction
of prototype
Deployment
delivery &
feedback
Often, a customer
defines a set of
general
objectives for
software,
but does not
identify detailed
requirements for
functions and
features

20. Evolutionary Models: Prototyping
 the prototyping paradigm assists you and other
stakeholders to better understand what is to be built
when requirements are fuzzy.
 “quick design” focuses on a representation of those
aspects of the software that will be visible to end users
(e.g., human interface layout or output display formats).
 The quick design leads to the construction of a
prototype.
 Ideally, the prototype serves as a mechanism for
identifying software requirements.
 The prototype can serve as “the first system.” built as
“throwaways,” others are evolutionary
20

21. Evolutionary Models:
Prototyping
 Problems:
 Stakeholders see what appears to be a working version of the
software
 As a software engineer, you often make implementation
compromises in order to get a prototype working quickly.
 The key is to define the rules of the game at the
beginning; that is, all stakeholders should agree that the
prototype is built to serve as a mechanism for defining
requirements. It is then discarded (at least in part), and
the actual software is engineered with an eye toward
quality.
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(McGraw-Hill 2009). Slides copyright 2009 by Roger Pressman. 21

22.  couples the iterative nature of prototyping with the
controlled and systematic aspects of the waterfall model
 Provides the potential for rapid development of
increasingly more complete versions of the software
 Anchor point milestones
 Each pass through the planning region results in
adjustments to the project plan.
 Cost, schedule, and the project manager adjusts the
planned number of iterations required to complete the
software.
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(McGraw-Hill 2009). Slides copyright 2009 by Roger Pressman. 22
Evolutionary Models: The Spiral

23. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009). Slides copyright 2009 by Roger Pressman. 23
Evolutionary Models: The Spiral
communication
planning
modeling
construction
deployment
delivery
feedback
start
analysis
design
code
test
estimation
scheduling
risk analysis

24. Evolutionary Models: The
Spiral
 In essence, the spiral, when characterized in this way,
remains operative until the software is retired
 Strengths:
 The spiral model is a realistic approach to the development of
large-scale systems and software.
 The spiral model uses prototyping as a risk reduction
mechanism
 enables you to apply the prototyping approach at any stage in
the evolution of the product.
 Weaknesses
 Evolutionary approach is controllable?
 demands considerable risk assessment expertise
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(McGraw-Hill 2009). Slides copyright 2009 by Roger Pressman. 24

25. Evolutionary Models: Concurrent
 The concurrent development model, sometimes called
concurrent engineering, allows a software team to represent
iterative and concurrent elements of any of the process
models
 For example, the modeling activity defined for the spiral model is
accomplished by invoking one or more of the following software
engineering actions: prototyping, analysis, and design.
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill 2009). Slides copyright 2009 by Roger Pressman. 25

26. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009). Slides copyright 2009 by Roger Pressman. 26
Evolutionary Models: Concurrent
Under review
Baselined
Done
Under
revision
Awaiting
changes
Under
development
none
Modeling activit y
represents the state
of a software engineering
activity or task

27. Comparison of different
life-cycle models
 The different software life cycle models can be compared from the
viewpoint of the customer. Initially, customer confidence in the
development team is usually high irrespective of the development
model followed. During the lengthy development process, customer
confidence normally drops off, as no working product is immediately
visible. Developers answer customer queries using technical slang,
and delays are announced. This gives rise to customer resentment. On
the other hand, an evolutionary approach lets the customer experiment
with a working product much earlier than the monolithic approaches.
Another important advantage of the incremental model is that it
reduces the customer’s trauma of getting used to an entirely new
system. The gradual introduction of the product via incremental phases
provides time to the customer to adjust to the new product. Also, from
the customer’s financial viewpoint, incremental development does not
require a large upfront capital outlay. The customer can order the
incremental versions as and when he can afford them.
These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill 2009). Slides copyright 2009 by Roger Pressman. 27

28. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009). Slides copyright 2009 by Roger Pressman. 28
Still Other Process Models
 Component based development—the process to
apply when reuse is a development objective
 Formal methods—emphasizes the mathematical
specification of requirements
 AOSD—provides a process and methodological
approach for defining, specifying, designing, and
constructing aspects
 Unified Process—a “use-case driven, architecture-
centric, iterative and incremental” software process
closely aligned with the Unified Modeling Language
(UML)

29. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009). Slides copyright 2009 by Roger Pressman. 29
The Unified Process (UP)
software increment
Release
Inception
Elaboration
construction
transition
production
inception
elaboration

30. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009). Slides copyright 2009 by Roger Pressman. 30
UP Phases
Inception Elaboration Construction Transition Production
UP Phases
Workflows
Requirements
Analysis
Design
Implementation
Test
Iterations #1 #2 #n-1 #n
Support

31. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009). Slides copyright 2009 by Roger Pressman. 31
UP Work Products
Inception phase
Elaboration phase
Construction phase
Transition phase
Vision document
Init ial use-case model
Init ial project glossary
Init ial business case
Init ial risk assessment .
Project plan,
phases and it erat ions.
Business model,
if necessary.
One or more prot ot ypes
I nc e pt i o
n
Use-case model
Supplement ary requirement s
including non-funct ional
Analysis model
Soft ware archit ect ure
Descript ion.
Execut able archit ect ural
prot ot ype.
Preliminary design model
Revised risk list
Project plan including
it erat ion plan
adapt ed workflows
milest ones
t echnical work product s
Preliminary user manual
Design model
Soft ware component s
Int egrat ed soft ware
increment
Test plan and procedure
Test cases
Support document at ion
user manuals
inst allat ion manuals
descript ion of current
increment
Delivered soft ware increment
Bet a t est report s
General user feedback

32. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009). Slides copyright 2009 by Roger Pressman. 32
Personal Software Process (PSP)
 Planning. This activity isolates requirements and develops both size and
resource estimates. In addition, a defect estimate (the number of defects
projected for the work) is made. All metrics are recorded on worksheets or
templates. Finally, development tasks are identified and a project schedule is
created.
 High-level design. External specifications for each component to be constructed
are developed and a component design is created. Prototypes are built when
uncertainty exists. All issues are recorded and tracked.
 High-level design review. Formal verification methods (Chapter 21) are applied
to uncover errors in the design. Metrics are maintained for all important tasks and
work results.
 Development. The component level design is refined and reviewed. Code is
generated, reviewed, compiled, and tested. Metrics are maintained for all
important tasks and work results.
 Postmortem. Using the measures and metrics collected (this is a substantial
amount of data that should be analyzed statistically), the effectiveness of the
process is determined. Measures and metrics should provide guidance for
modifying the process to improve its effectiveness.

33. These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009). Slides copyright 2009 by Roger Pressman. 33
Team Software Process (TSP)
 Build self-directed teams that plan and track their work,
establish goals, and own their processes and plans.
These can be pure software teams or integrated product
teams (IPT) of three to about 20 engineers.
 Show managers how to coach and motivate their teams
and how to help them sustain peak performance.
 Accelerate software process improvement by making
CMM Level 5 behavior normal and expected.
 The Capability Maturity Model (CMM), a measure of the
effectiveness of a software process, is discussed in Chapter 30.
 Provide improvement guidance to high-maturity
organizations.
 Facilitate university teaching of industrial-grade team
skills.