Software Engineering.ppt

Unit 1 syllabus
• Introduction to Software Engineering : The
evolving role of software, Changing Nature of
Software, Software myths.
• A Generic view of process : Software
engineering- A layered technology, a process
framework, The Capability Maturity Model
Integration (CMMI), Process patterns, process
assessment, personal and team process
models.
1

INDEX
Unit-1
S.No Topic Lecture No PPTSlides
1
Introduction to software
Engineering: Evolving role
software
L1 3
2 The changing nature of
software & legacy software
L2 10
3 Software myths L3 15
4 A generic view of process:
Software Engineering-A layered
technology
L4 19
5 A Process Framework L5
22
5 The Capability maturity model
Integration(CMMI)
L6 25
6 Process Patterns, Process
assessment
L7
31
7 Personal and Team Process
models
L8 35
2

Introduction to software Engineering
The Evolving role of software
• Dual role of Software
A Product
- Information transformer-
producing, managing and displaying
A Vehicle for delivering a product
- Control of computer(operating system),the
communication of information(networks) and
the creation of other programs
3

• Software is defined as
1. Instructions
- Programs that when executed provide
desired function
2. Data structures
-Enable the programs to adequately
manipulate information
3. Documents
-Describe the operation and use of the
programs.
4

• Definition of Engineering
-Application of science, tools and methods
to find cost effective solution to problems
Definition of SOFTWARE ENGINEERING
- SE is defined as systematic, disciplined and
quantifiable approach for the development, operation
and maintenance of software
5

Characteristics of software
• Software is developed or engineered, it is not
manufactured in the classical sense.
• Software does not wear out. However it
deteriorates due to change.
• Software is custom built rather than
assembling existing components.
-Although the industry is moving towards
component based construction, most software
continues to be custom built
6

CHARACTERISTICS OF HARDWARE
Failure
rate
Time
“Infant
mortality” “Wear out”
Fig: FAILURE CURVE FOR HARDWARE
7

CHARACTERISTICS OF SOFTWARE
Fig: FAILURE CURVE FOR SOFTWARE
8

THE CHANGING NATURE OF
SOFTWARE
• Seven Broad Categories of software are
challenges for software engineers
 System software
 Application software
 Engineering and scientific software
 Embedded software
 Product-line software
 Web-applications
 Artificial intelligence software
9

THE CHANGING NATURE OF
SOFTWARE
• System software. System software is a collection of programs
written to service other programs
• Embedded software
-- resides in read-only memory
--is used to control products and systems for the consumer and
industrial markets.
• Artificial intelligence software. Artificial intelligence (AI) software
makes use of nonnumeric algorithms to solve complex problems
that are not amenable to computation or straightforward analysis
• Engineering and scientific software. Engineering and scientific
software have been characterized by "number crunching"
algorithms.
10

LEGACY SOFTWARE
• Legacy software are older programs that
are developed decades ago.
• The quality of legacy software is poor
because it has inextensible
design,convoluted code,poor and
nonexistent documentation,test cases and
results that are not achieved.
11

• As time passes legacy systems evolve
due to following reasons:
The software must be adapted to meet the
needs of new computing environment or
technology.
The software must be enhanced to implement
new business requirements.
The software must be extended to make it
interoperable with more modern systems or
database
The software must be rearchitected to make it
viable within a network environment.
12

Software Evolution
• Software evolves due to changes
• Changes occur due to correction,adaption and enhancement
• 8 Laws of unified theory
 The Law of Continuing Change.
 The Law of Increasing Complexity.
 The Law of Self-Regulation
 The Law of Conservation of Organizational Stability.
 The Law of Conservation of Familiarity
 The Law of Continuing Growth
 The Law of Declining Quality
 The Feedback System Law
13

SOFTWARE MYTHS
• Widely held but false view
• Propagate misinformation and confusion
• Three types of myth
- Management myth
- Customer myth
- Practitioner’s myth
14

MANAGEMENT MYTHS
• Myth(1)
-The available standards and procedures
for software are enough.
• Myth(2)
-Each organization feel that they have state-of-art
software development tools since they have latest
computer.
• Myth(3)
-Adding more programmers when the work is behind
schedule can catch up.
• Myth(4)
-Outsourcing the software project to third party, we can
relax and let that party build it.
15

CUSTOMER MYTH
• Myth(1)
- General statement of objective is
enough to begin writing programs, the
details can be filled in later.
• Myth(2)
-Software is easy to change because
software is flexible
16

PRACTITIONER’S MYTH
• Myth(1)
-Once the program is written, the job has been done.
• Myth(2)
-Until the program is running, there is no way of
assessing the quality.
• Myth(3)
-The only deliverable work product is the working
program
• Myth(4)
-Software Engineering creates voluminous and
unnecessary documentation and invariably slows down
software development.
17

SOFTWARE ENGINEERING-A LAYERED
TECHNOLOGY
18
Fig: Software Engineering-A layered technology

SOFTWARE ENGINEERING-A
LAYERED TECHNOLOGY
• Quality focus
- Bedrock that supports software
Engineering.
• Process
- Foundation for software Engineering
• Methods
- Provide technical How-to’s for building
software
• Tools
- Provide semi-automatic and automatic
support to methods
19

A PROCESS FRAMEWORK
• Establishes the foundation for a complete
software process
• Identifies a number of framework activities
applicable to all software projects
• Also include a set of umbrella activities
that are applicable across the entire
software process.
20

A PROCESS FRAMEWORK
Common process framework
Umbrella activities
Framework activities
TTTasks
Milestones,delierables
SQA points
21

A PROCESS FRAMEWORK
• Used as a basis for the description of
process models
• Generic process activities
Communication
Planning
Modeling
Construction
Deployment
22

A PROCESS FRAMEWORK
• Generic view of engineering complimented
by a number of umbrella activities
– Software project tracking and control
– Formal technical reviews
– Software quality assurance
– Software configuration management
– Document preparation and production
– Reusability management
– Measurement
– Risk management
23

CAPABILITY MATURITY MODEL
INTEGRATION(CMMI)
• Developed by SEI(Software Engineering institute)
• Assess the process model followed by an organization and rate the
organization with different levels
• A set of software engineering capabilities should be present as
organizations reach different levels of process capability and
maturity.
• CMMI process meta model can be represented in different ways
1.A continuous model
2.A staged model
Continuous model:
-Lets organization select specific improvement that best meet its
business objectives and minimize risk
-Levels are called capability levels.
-Describes a process in 2 dimensions
-Each process area is assessed against specific goals and practices
and is rated according to the following capability
levels. 24

CMMI
• Six levels of CMMI
– Level 0:Incomplete
– Level 1:Performed
– Level 2:Managed
– Level 3:Defined
– Level 4:Quantitatively managed
– Level 5:Optimized
25

CMMI
• INCOMPLETE
-Process is adhoc.Objective and goal of process areas are not known
• Performed
-Goal,objective,work tasks,work products and other activities of software
process are carried out
• Managed
-Activities are monitored, reviewed, evaluated and controlled
• Defined
-Activities are standardized, integrated and documented
• Quantitatively Managed
-Metrics and indicators are available to measure the process and quality
• Optimized
- Continuous process improvement based on quantitative feed back from
the user
-Use of innovative ideas and techniques, statistical quality control and other
methods for process improvement.
26

CMMI
Staged model
- This model is used if you have no clue of how to improve the
process for quality software.
- It gives a suggestion of what things other organizations have
found helpful to work first
- Levels are called maturity levels
27

LEVEL FOCUS PROCESS AREA
Optimizing Continuous process
Improvement
-Organizational Innovation and
Deployment
-Causal Analysis and Resolution
Quantitatively
managed
Quantitative
management
-Organizational process performance
-Quantitative project management
Defined Process standardized Requirements Development
Technical Solution
Product Integration
Verification
Validation
Organizational Process Focus
Organizational Process Definition
Organizational Training
Integrated Project Management
Risk Management
28

−Integrated Teaming
−Integrated Supplier
Management
−Decision Analysis and
Resolution
−Organizational
Environment for Integration
Managed Basic project management Requirements Management
Project Planning
Project Monitoring and
Control
Supplier Agreement
Measurement and Analysis
Process and Product
Quality Assurance
Configuration Management
Performed
29

PROCESS PATTERNS
• Software Process is defined as collection of Patterns
• Process pattern provides a template
• Process Template
-Pattern Name
-Intent
-Type
-Task pattern
- Stage pattern
-Phase Pattern
• Initial Context
• Problem
• Solution
• Resulting Context
• Related Patterns
30

PROCESS ASSESSMENT
• Does not specify the quality of the
software or whether the software will be
delivered on time or will it stand up to the
user requirements.
• It attempts to keep a check on the current
state of the software process with the
intention of improving it.
31

PROCESS ASSESSMENT
Software Process
Software Process
Assessment
Software Process
improvement
Capability determination
Motivates

APPROACHES TO SOFTWRE
ASSESSMENT
• Standard CMMI assessment (SCAMPI)
• CMM based appraisal for internal process
improvement
• SPICE(ISO/IEC 15504)
• ISO 9001:2000 for software
33

Personal and Team Software Process
• Personal software process
PLANNING
HIGH LEVEL DESIGN
HIGH LEVEL DESIGN REVIEW
DEVELOPMENT
POSTMORTEM
34

Personal and Team Software Process
• Team software process
 Goal of TSP
- Build self-directed teams
- Motivate the teams
- Acceptance of CMM level 5 behavior as
normal to accelerate software process
improvement
- Provide improvement guidance to high
maturity organization
35

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