PUNE and BPUT University ,, Teaching Material

1. UNIT I
Introduction to Software Engineering
Presented By
Prof.Hitesh Mohapatra
Dept. of Computer Engg.

2. Software’s Dual Role

Software is a product

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Delivers computing potential
Produces, manages, acquires, modifies, displays, or transmits
information
Software is a vehicle for delivering a product

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Supports or directly provides system functionality
Controls other programs (e.g., an operating system)
Effects communications (e.g., networking software)
Helps build other software (e.g., software tools)

3. What is Software?
Software is a set of items or objects
that form a “configuration” that
includes
• programs
• documents
• data ...

4. What is Software?


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software is engineered
software doesn’t wear out
software is complex

5. Wear vs. Deterioration
in re s d fa re
c ae
ilu
ra d e to s e e c
te u
id ffe ts
F ilue
a r
rt
ae
cag
hne
a t ac r e
cu l uv
id a e c r e
e liz d uv
T e
im

6. Software Applications

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system software
application software
engineering/scientific software
embedded software
product-line software
Web Apps (Web applications)
AI software

7. Software—New Categories

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Ubiquitous computing—wireless networks
Net sourcing—the Web as a computing engine
Open source—”free” source code open to the computing
community (a blessing, but also a potential curse!)
Also … (see Chapter 32)
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Data mining
Grid computing
Cognitive machines
Software for nanotechnologies

8. Legacy Software
Why must it change?

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software must be adapted to meet the needs of new
computing environments or technology.
software must be enhanced to implement new
business requirements.
software must be extended to make it interoperable
with other more modern systems or databases.
software must be re-architected to make it viable
within a network environment.

9. Software Myths

Management Myths
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Customer myths
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We have books of standards, my staff will have sufficient info.
I work very hard to put the latest, greatest, fastest, state-of-the-art
hardware in front of all my programmers.
We have the greatest CASE tools around.
If we get behind, we can just add more programmers.
A general statement of objectives is sufficient to start coding, fill in the
details later.
Project requirements change constantly, but change is easy because
software is flexible.
Programmer myths
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Once the program is written and working, our job is done.
Until the program is running, there is no way to assess quality.
The only deliverable for a successful project is the working program.

10. Software Engineering
Practice
Software engineering practice
- Communication practices
- Planning practices
- Analysis modeling practices
- Design modeling practices
- Construction practices
- Deployment practices
-

11. Software Engineering Practice
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Consists of a collection of concepts, principles, methods, and tools
that a software engineer calls upon on a daily basis
Equips managers to manage software projects and software
engineers to build computer programs
Provides necessary technical and management how to’s in getting
the job done
Transforms a haphazard unfocused approach into something that is
more organized, more effective, and more likely to achieve success

12. The Essence of Problem Solving
Understand the problem (communication and analysis)
1)
•
•
•
•
Who has a stake in the solution to the problem?
What are the unknowns (data, function, behavior)?
Can the problem be compartmentalized?
Can the problem be represented graphically?
Plan a solution (planning, modeling and software design)
1)
•
•
•
Have you seen similar problems like this before?
Has a similar problem been solved and is the solution reusable?
Can sub problems be defined and are solutions available for the
sub problems?

13. The Essence of Problem Solving
(continued)
Carry out the plan (construction; code generation)
3)
•
•
Does the solution conform to the plan? Is the source code
traceable back to the design?
Is each component of the solution correct? Has the design and
code been reviewed?
Examine the results for accuracy (testing and quality
assurance)
3)
•
•
Is it possible to test each component of the solution?
Does the solution produce results that conform to the data,
function, and behavior that are required?

14. Seven Core Principles for Software Engineering
1)
Remember the reason that the software exists
•
1)
Keep it simple, stupid (KISS)
•
1)
Never design yourself into a corner; build software that can be easily
changed and adapted
Plan ahead for software reuse
•
1)
Always specify, design, and implement knowing that someone else will
later have to understand and modify what you did
Be open to the future
•
1)
A clear vision is essential to the project’s success
Others will consume what you produce
•
1)
All design and implementation should be as simple as possible
Maintain the vision of the project
•
1)
The software should provide value to its users and satisfy the
requirements
Reuse of software reduces the long-term cost and increases the value of
the program and the reusable components
Think, then act
•
Placing clear, complete thought before action will almost always
produce better results

15. Communication Practices
(Requirements Elicitation)
Communication
Project initiation
Requirements
gathering
Planning
Estimating
Scheduling Modelling
Analysis
Tracking
Design
Construction
Code Test
Deployment
Delivery
Support
Feedback
15

16. Communication Principles
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
Listen to the speaker and concentrate on what is being said
Prepare before you meet by researching and understanding the
problem
Someone should facility the meeting and have an agenda
Face-to-face communication is best, but also have a document or
presentation to focus the discussion
Take notes and document decisions
Strive for collaboration and consensus
Stay focused on a topic; modularize your discussion
If something is unclear, draw a picture
Move on to the next topic a) after you agree to something, b) if you
cannot agree to something, or c) if a feature or function is unclear
and cannot be clarified at the moment
Negotiation is not a contest or a game; it works best when both
parties win

17. Planning Practices
(Defining a Road Map)
Communication
Project initiation
Requirements
gathering
Planning
Estimating
Scheduling
Modelling
Tracking
Analysis
Design
Construction
Code
Test
Deployment
Delivery
Support
Feedback
17

18. Planning Principles
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
Understand the scope of the project
Involve the customer in the planning activity
Recognize that planning is iterative; things will change
Estimate based only on what you know
Consider risk as you define the plan
Be realistic on how much can be done each day by each person
and how well
Adjust granularity as you define the plan
Define how you intend to ensure quality
Describe how you intend to accommodate change
Track the plan frequently and make adjustments as required

19. Barry Boehm’s W5HH Principle
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Why is the system being developed?
What will be done?
When will it be accomplished?
Who is responsible for each function?
Where are they organizationally located?
How will the job be done technically and managerially?
How much of each resource is needed?
The answers to these questions lead to a definition of key
project characteristics and the resultant project plan.

20. Modeling Practices
(Analysis and Design)
Communication
Project initiation
Requirements
gathering
Planning
Estimating
Scheduling
Tracking
Modelling
Analysis
Design
Construction
Code
Test
Deployment
Delivery
Support
Feedback

21. Analysis Modeling Principles
1)
2)
3)
4)
5)
The information domain of a problem (the data that flows in and
out of a system) must be represented and understood
The functions that the software performs must be defined
The behavior of the software (as a consequence of external events)
must be represented
The models that depict information, function, and behavior must
be partitioned in a manner that uncovers detail in a layered (or
hierarchical) fashion
The analysis task should move from essential information toward
implementation detail

22. Design Modeling Principles
1)
2)
3)
4)
5)
6)
7)
8)
9)
The design should be traceable to the analysis model
Always consider the software architecture of the system to be built
Design of data is as important as design of processing functions
Interfaces (both internal and external) must be designed with care
User interface design should be tuned to the needs of the end-user
and should stress ease of use
Component-level design should be functionally independent (high
cohesion)
Components should be loosely coupled to one another and to the
external environment
Design representations (models) should be easily understandable
The design should be developed iteratively; with each iteration, the
designer should strive for greater simplicity
External quality factors: those properties that can be readily
observed
Internal quality factors: those properties that lead to a high-quality
design from a technical perspective

23. Construction Practices
Communication
Project initiation
Requirements
gathering
Planning
Estimating
Scheduling
Tracking
Modelling
Analysis
Constructio
Design
n
Code
Test Deployment
Delivery
Support
Feedback

24. Coding Principles
(Preparation before coding)
1)
2)
3)
4)
5)
Understand the problem you are trying to solve
Understand basic design principles and concepts
Pick a programming language that meets the needs of the
software to be built and the environment in which it will operate
Select a programming environment that provides tools that will
make your work easier
Create a set of unit tests that will be applied once the component
you code is completed

25. Coding Principles
(As you begin coding)
1)
2)
3)
4)
5)
6)
7)
8)
Constrain your algorithms by following structured programming
practices
Select data structures that will meet the needs of the design
Understand the software architecture and create interfaces that are
consistent with it
Keep conditional logic as simple as possible
Create nested loops in a way that makes them easily testable
Select meaningful variable names and follow other local coding
standards
Write code that is self-documenting
Create a visual layout (e.g., indentation and blank lines) that aids
code understanding

26. Coding Principles
1)
2)
3)
(After completing the first round of
code)
Conduct a code walkthrough
Perform unit tests (black-box and white-box) and correct errors
you have uncovered
Refactor the code

27. Testing Principles
1)
2)
3)
All tests should be traceable to the software requirements
Tests should be planned long before testing begins
The Pareto principle applies to software testing
•
1)
Testing should begin “in the small” and progress toward testing
“in the large”
•
1)
80% of the uncovered errors are in 20% of the code
Unit testing --> integration testing --> validation testing --> system
testing
Exhaustive testing is not possible .

28. Test Objectives
1)
2)
3)
Testing is a process of executing a program with the intent of
finding an error
A good test case is one that has a high probability of finding an asyet undiscovered error
A successful test is one that uncovers an as-yet undiscovered error

29. Deployment Practices
Communication
Project initiation
Requirements
gathering
Planning
Estimating
Scheduling
Tracking Modelling
Analysis
Design Construction
Code
Test Deployment
Delivery
Support
Feedback

30. Deployment Principles
1)
Customer expectations for the software must be managed
•
1)
2)
3)
4)
Be careful not to promise too much or to mislead the user
A complete delivery package should be assembled and tested
A support regime must be established before the software is
delivered
Appropriate instructional materials must be provided to end
users
Buggy software should be fixed first, delivered later

31. Software Process

32. Process Models
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Waterfall model
Incremental Process Models
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Evolutionary Process Models
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Prototyping model
Spiral model
Specialized Process Models
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Rapid application development model
Incremental model
Component-Based Development
Formal Method model
Comparison of life-cycle models

33. Waterfall model
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Requirements are reasonably understood.
When work flow is linear in fashion
Systematic sequential approach

34. r)
r)
(o e (o el
l
de y cl M od
o c
l M ife ti a l
l
rfa a l L ue n
a te sic e q
W as
S
C l ne a r
Li

36. Incremental model
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Evolution of waterfall model
New features added to 1st Increment(core product)
Incremental software development model may be
applicable to projects where:
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Software Requirements are well defined, but realization may be
delayed.
The basic software functionality are required early

37. SW Functionality and features
Time
Inc 1
Inc 2
Inc 3

38. RAD Model
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Rapid Application Development
Short development cycle
Faster development (60-90) days
High quality results
Use of (CASE) Tools
Component based construction
System delivered in short time (2 to 3 months)
Useful where requirements are well understood and
scope is limited

39. The RAD Model
Team # n
M o d e lin g
bus ines s m odeling
dat a m odeling
proc es s m odeling
C o n s t r u c t io n
c om ponent reus e
aut om at ic c ode
generat ion
t es t ing
Team # 2
Com m unicat ion
Mo d eling
b u si n e ss m o d e l i n g
dat a m odeling
p ro ce ss m o d e l i n g
Planning
Co nst r uct io n
Team # 1
co m p o n e n t re u se
a u t o m a t i c co d e
g e n e ra t i o n
t e st i n g
Mode ling
De ploym e nt
int egrat ion
deliv ery
feedback
business modeling
dat a modeling
process modeling
Const r uct ion
component reuse
aut omat ic code
generat ion
t est ing
6 0 - 9 0 days
40

40. Process Models
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Waterfall model
Incremental Process Models
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Evolutionary Process Models
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Prototyping model
Spiral model
Specialized Process Models
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Rapid application development model
Incremental model
Component-Based Development
Formal Method model
Unified Process
Comparison of life-cycle models

41. Prototyping
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Early approximation of a final system
Linear and iterative
Customer is unable to define the system
Requirements are not freezed
a prototype is built to understand the requirements

42. Evolutionary Models: Prototyping
Qu ick p lan
Quick
Com m unicat ion
plan
communication
Mo d e lin g
Modeling
Qu ick d e sig n
Quick design
Deployment
Deployment
De live r y
delivery &
& Fe e dback
feedback
Const r uct ion
Construction
of
of prototype
pr ot ot ype
43

43. Spiral Model
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Simplified form
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Precede each phase by
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Waterfall model plus risk analysis
Alternatives
Risk analysis
Follow each phase by

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Evaluation
Planning of next phase

44. Evolutionary Models: The Spiral
planning
estimation
scheduling
risk analysis
communication
modeling
analysis
design
start
deployment
delivery
feedback
construction
code
test
45

45. Specialized Process Models
1)Component Based Development
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COTS
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Commercial off-the-shelf software components developed by
vendors who offer them as products.
Decomposition of the engineered systems into functional
or logical components with well-defined interfaces used
for communication across the components.

46. Co
De m
M s ig p on
C o odu n e n
m le a r c t i n
pr I n h te
e h te ite g
e n ge ct u r a t
s i ra r e ion
ve tio
te n.
st
in
g.

47. 2) Formal Methods Model
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Mathematically based techniques for representing and
analysis of software.
Formal methods include
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Formal specification
Specification analysis and proof
Transformational development
Program verification

48. Formal Methods Model
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Reduces requirements errors as it forces a detailed
analysis of the requirements
Incompleteness and inconsistencies can be
discovered and resolved
Currently very time consuming and expensive
Extensive training required
Difficult to use this model to communicate with the
customer.

49. Unified Process
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Contains features of OOA and OOD.
UML- Unified Modeling Language
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It was created to support the OO design and modeling.
iterative and incremental process

50. Phases of Unified process
All the phases are concurrent in nature
 Inception
 Elaboration
 Construction
 Transition
 Production

51. The Unified Process (UP)
Elab o r at io n
elaboration
Incep t
inceptionio n
inception
co nst r uct io n
Release
soft ware increment
t r ansit io n
p r o d uct io n
52

52. UP (contd)

Inception
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Customer communication
Planning
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Business requirements are identified
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Identify resources, assess risks, defines schedule
In the form of use cases.
Rough architecture

A tentative outline of major sub-systems, functions and features
that populate them.

53. UP (contd)

Elaboration
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Customer communication
Modeling activity
Expands the use cases.
Expands the architecture to:


Use case model, analysis model, design model, implementation
model and deployment model.
Review plan and make modifications

Evaluate scope, risks, project delivery dates

54. UP (contd)

Construction

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
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Develop software components (that make the use cases
operational).
Complete the analysis and design models.
Implement all functions and features for that increment.
Conduct unit testing for the components
Integrate components.

55. UP (contd)

Transition
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Create user manuals, guidelines, installation procedures.
Software is given to users for beta testing.
Get user feedback
The increment is now a useable software release.

56. Incept ion 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 y pes
I nc e pt i o
n
UP Work Products
Elaborat ion phase
Use-case model
Supplement ary requirement s
including non-funct ional
Analy sis model
Soft ware archit ect ure
Descript ion.
Execut able archit ect ural
prot ot y pe.
Preliminary design model
Rev ised risk list
Project plan including
it erat ion plan
adapt ed workflows
milest ones
t echnical work product s
Preliminary user manual
Const ruct ion phase
Design model
Sof t 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
Transit ion phase
Deliv ered soft ware increment
Bet a t est report s
General user feedback
57

57. Agile Software Development
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
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Is a group of software development methodologies
based on iterative and incremental development, where
requirements and solutions evolve through
collaboration between self-organizing, cross-functional
teams.
Self Organization: is the process where a structure or
pattern appears in a system without central authority.
Cross-Functional team : is a group of people with
different functional expertise working toward a common
goal.

58. Extreme Programming



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Is a software development methodology which is
intended to improve software quality and
responsiveness to changing customer requirements.
It releases product in short development cycles (time
boxing)
Pair Programming: Driver and Observer
Time Boxing
Code Review
Unit Testing