Se Session 1

8/12/2019 Se Session 1

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Copyright Amity University

MSc-(IT)

Software Engineering

Semester - I


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Faculty Profile

MSc (Computer Science)

CCNA (Cisco certified Network Associate)

CCNA (Cisco certified )

Ph D (CSE) (Thesis Submitted)

Publications

International/ National Journal = 8 (including ACM, ISJKE)

International/ National Conference = 9 (including Springer)

Conference/ Workshop Attended

Bangkok

Vietnam


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Patents filed provisionally

ANN model

Area of specialization

Software Engineering

Artificial IntelligenceExperience

5 + teaching

1 research

Member

Cisco (Academic Council, USA)

Cisco (Learning Institute, USA)


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Why We Need Software

Engineering?

Change in nature & complexity of software

Concept of one guru is over

We all want improvement


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Why Software Engineering? Software development is hard!

Important to distinguish easy systems (onedeveloper, one user, experimental use only) fromhard systems (multiple developers, multiple users,

products) Experience with easy systems is misleading

One person techniques do not scale up

Analogy with bridge building:

Over a stream = easy, one person job Over River Severn ? (the techniques do not scale)


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Software Crisis!

over budget

53%

success

16%failure

31%


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Software Crises

As per the IBM report, 31%of the project get

cancelled before they are completed, 53% over-

run their cost estimates by an average of 189%

and for every 100 projects, there are 94 restarts.



Factors Contributing Software Crises

Larger problems,

Lack of adequate training in software

engineering Increasing skill shortage,

Low productivity improvements


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Some Software failuresIt took the European Space Agency 10 years and $7

billion to produce Ariane 5, a giant rocket capable of

hurling a pair of three-ton satellites into orbit with each

launch and intended to give Europe overwhelming

supremacy in the commercial space business.

Ariane 5

The rocket was destroyed after 39 seconds of its launch,at an altitude of two and a half miles along with its

payload of four expensive and uninsured scientific

satellites.


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When the guidance systems own computer

tried to convert one piece of data thesideways velocity of the rocket from a 64 bit

format to a 16 bit format; the number was too

big, and an overflow error resulted after 36.7

seconds. When the guidance system

shutdown, it passed control to an identical,

redundant unit, which was there to providebackup in case of just such a failure.

Unfortunately, the second unit, which had

failed in the identical manner a few

milliseconds before.

Some Software failures


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Y2K problem:

It was simply the ignorance about the adequacy

or otherwise of using only last two digits of the

year.

The 4-digit date format, like 1964, was shortened

to 2-digit format, like 64.



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The Patriot Missileo First time used in Gulf war

Reasons:

A small timing error in the systemsclock accumulated

to the point that after 14 hours, the tracking systemwas no longer accurate. In the Dhahran attack, the

system had been operating for more than 100 hours.

o Used as a defense from Iraqi Scud missiles

o Failed several times including one that killed 28 US

soldiers in Dhahran, Saudi Arabia



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Part of an abort scenario for

the Shuttle requires fuel

dumps to lighten thespacecraft. It was during the

second of these dumps that a

(software) crash occurred.

...the fuel management

module, which had performed

one dump and successfully

exited, restarted when recalled

for the second fuel dump...

The Space Shuttle



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Some Software failuresWindows XP

o Microsoft released Windows XP on October 25, 2001.

o On the same day company posted 18 MB of

compatibility patches on the website for bug fixes,

compatibility updates, and enhancements.

o Two patches fixed important security holes.



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What is software? It is defined as Computer programs

and associated documentation


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Programs

Operating

ProceduresDocumentatio

n

Software=Program+Documentation+Operating Procedures

Components of software

What is software?


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What are the attributes of good software?

The software should deliver the required functionality and

performance to the user and should be maintainable, dependable

and usable

Maintainability Software must evolve to meet changing needs

Dependability Software must be trustworthy

Efficiency Software should not make wasteful use of system resources

Usability Software must be usable by the users for which it was designed


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Documentation

Manuals

Analysis

/Specification

Design

Implementation

Testing

Formal Specification

Context-Diagram

Data FlowDiagrams

Flow Charts

Entity-RelationshipDiagram

Source Code Listings

Cross-Reference

ListingTest Data

Test Results

Documentation consists of different types of manuals are

List of documentation manuals


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OperatingProcedures

User

Manuals

Operational

Manuals

System Overview

Beginners Guide

Tutorial

Reference Guide

Installation Guide

System

Administration Guide

List of operating procedure manuals.

Documentation consists of different types of manuals are


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What is a software

process?

A set of activitieswhose goal is the development orevolution of software

Generic activities in all software processes are:

Specification- what the system should do and itsdevelopment constraints

Development- production of the software system

Validation- checking that the software is what the customer

wants Evolution- changing the software in response to changing

demands


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What is a software process model?A simplified representation of a software process,presented from a specific perspective

Examples of process perspectives:Workflow perspective represents inputs, outputs and dependencies

Data-flow perspective represents data transformation activitiesRole/action perspectiverepresents the roles/activities of the

people involved in software process

Generic process models Waterfall

Evolutionary development

Formal transformation

Integration from reusable components


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Software products may be developed for a particularcustomer or may be developed for a general market

Software Product

Software productsmay beGeneric- developed to be sold to a range of different customers

Bespoke(custom) - developed for a single customer according to their specification



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What is software engineering?Software engineering is an engineering discipline which isconcerned with all aspects of software production

Software engineersshould

adopt a systematic and organised approach to their

work

use appropriate tools and techniques depending on

the problem to be solved, the development constraints and

use the resources available


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At the first conference on software engineering in 1968, Fritz Bauer defined software

engineering as Theestablishment and use of sound engineering principles in order to

obtain economically developed software that is reliable and works efficiently on real

machines.

Stephen Schach defined the same as Adiscipline whose aim is the production of quality

software, software that is delivered on time, within budget, and that satisfies its

requirements.

Both the definitions are popular and acceptable to majority. However, due to increase in

cost of maintaining software, objective is now shifting to produce quality software that is

maintainable, delivered on time, within budget, and also satisfies its requirements.

What is software engineering?


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Software ProcessThe software process is the way in which we produce

software.

Why is it difficult to improve software process ?

Not enough time

Lack of knowledge


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Learning curve

Do not quit here!

Improved future stateProcess improvement

beginsInitial state

state

Productivity

Time

Wrong motivations

Software Process

Insufficient commitment


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Software CharacteristicsSoftware does not wear out.

Useful life

phase

Wear outphase

Burn-in

phase

Failure

Intensity

Time


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Software is not manufactured

Software Characteristics Reusability of components

Software is flexible


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Comparison of constructing a bridge vis--vis writing a program.

Sr.

No

Constructing a bridge Writing a program

1.

2.

3.

4.

5.

6.

7.

Software Characteristics

The problem is well understoodOnly some parts of the problem are

understood, others are not

There are many existing bridges

The requirement for a bridge typically do

not change much during construction

The strength and stability of a bridge can be

calculated with reasonable precision

When a bridge collapses, there is a

detailed investigation and report

Engineers have been constructing bridgesfor thousands of years

Materials (wood, stone,iron, steel) and

techniques (making joints in wood, carving

stone, casting iron) change slowly.

Every program is different and designed for

special applications.

Requirements typically change during allphases of development.

Not possible to calculate correctness of a

program with existing methods.

When a program fails, the reasons are often

unavailable or even deliberately concealed.

Developers have been writing programsfor 50 years or so.

Hardware and software changes rapidly.


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SystemSoftware

Real TimeSoftware

EmbeddedSoftware

Engineeringand ScientificSoftware

Web basedSoftware

ArtificialIntelligence

SoftwarePersonal

ComputerSoftware

BusinessSoftware

Software Applications


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The Changing Nature of SoftwareTrend has emerged to provide source code to the

customer and organizations.

Software where source codes are available are known

as open source software.

Examples

Open source software: LINUX, MySQL, PHP, Open office, Apache webserver etc.


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Management may be confident about good

standards and clear procedures of the

company.But the taste of any food item

is in the eating;not in the Recipe!

Software Myths Management Perspectives)


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Company has latest computers and state-

of-the-art software tools, so we shouldnt

worry about the quality of the product.

The infrastructure isonly one of the several factors

that determine the qualityof the product!



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Addition of more software specialists, those with

higher skills and longer experience may bring the

schedule back on the track!

Unfortunately,that may further delay the schedule!



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Software is easy to change

The reality is totally different.



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A general statement of objectives is sufficient to get

started with the development of software. Missing/vague

requirements can easily be incorporated/detailed out as

they get concretized.

If we do so, we are headingtowards a disaster.

Software Myths Customer Perspectives)


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Software with more features is better

software

Software can work right the first time

Both are only myths!

Software Myths Customer Perspectives)


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Once the software is demonstrated, the job is

done.

Usually, the problems just begin!

Software Myths Developer Perspectives)


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Software quality can not be assessed before

testing.

However, quality assessment techniquesshould be used through out thesoftware development life cycle.



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The only deliverable for a softwaredevelopment project is the tested code.

Tested code is only one of the deliverable!



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Aim is to develop working programs

Those days are over. Now objective is todevelop good quality maintainable

programs!



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Some Terminologies Deliverablesand Milestones

Different deliverables are generated during software development. The examples are

source code, user manuals, operating procedure manuals etc.

The milestones are the events that are used to ascertain the status of the project.

Finalization of specification is a milestone. Completion of design documentation is another

milestone. The milestones are essential for project planning and management.


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Productand Process

Some TerminologiesProduct: What is delivered to the customer, is called a product. It may include source code,

specification document, manuals, documentation etc. Basically, it is nothing but a set of

deliverables only.

Process: Process is the way in which we produce software. It is the collection of activities

that leads to (a part of) a product. An efficient process is required to produce good quality

products.

If the process is weak, the end product will undoubtedly suffer, but an obsessive over

reliance on process is also dangerous.


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Some Terminologies Measures, Metricsand Measurement

A measure provides a quantitative indication of the extent, dimension, size, capacity,

efficiency, productivity or reliability of some attributes of a product or process.

Measurement is the act of evaluating a measure.

A metric is a quantitative measure of the degree to which a system, component or process

possesses a given attribute.


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Some Terminologies Software Processand Product Metrics

Process metrics quantify the attributes of software development process and environment;

whereas product metrics are measures for the software product.

Examples

Process metrics: Productivity, Quality, Efficiency etc.

Product metrics: Size, Reliability, Complexity etc.


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Productivityand Effort

Productivity is defined as the rate of output, or production per unit of effort, i.e. the output

achieved with regard to the time taken but irrespective of the cost incurred.

Hence most appropriate unit of effort is Person Months (PMs), meaning thereby number of

persons involved for specified months. So, productivity may be measured as LOC/PM (lines

of code produced/person month)

Some Terminologies


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Some Terminologies Module and Software Components

There are many definitions of the term module. They range from amodule is a FORTRAN

subroutineto amodule is an Ada Package,to Proceduresand functions of PASCAL andC, to C++ Java classes to Javapackages to amodule is a work assignment for an

individual developer. All these definition are correct. The term subprogram is also used

sometimes in place of module.


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An independently deliverable piece of functionality providing access to its services

through interfaces.

Acomponent represents a modular, deployable, and replaceable part of a system that

encapsulates implementation and exposes a set of interfaces.

Some Terminologies


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Some Terminologies Genericand CustomizedSoftware Products

Generic products are developed for anonymous customers. The target is generally the

entire world and many copies are expected to be sold. Infrastructure software like

operating system, compilers, analyzers, word processors, CASE tools etc. are covered in thiscategory.

The customized products are developed for particular customers. The specific product is

designed and developed as per customer requirements. Most of the developmentprojects (say about 80%)come under this category.


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Role of Management in Software Development

Factors

People

Product Process

Project


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Dependency

Order

Project Product

Process

People

1

2

3

4

Role of Management in Software Development


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Software Development Life Cycle

Requirement Analysis &

Specification

Design

Coding

TestingMaintenance & Operations


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Software Life Cycle Model

Waterfall Model

Prototype Model

Iterative Enhancement Model Evolutionary Development Model

Spiral Model

Rapid Application Development (RAD) Model

Waterfall Model


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Waterfall Model

Linear Sequential Model

Classical Life Cycle ModelR e qu ir e m e nt

Design

I m pl e m e nt a t io na nd u ni t t e st in g

I nt e gr a t io n a n ds ys te m t e st in g

Operation &

Maintenance


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Problems with the Waterfall Model

It is difficult to define all requirements at the beginning of

a project

This model is not suitable for accommodating any

change

A working version of the system is not seen until late in

the projectslife

It does not scale up well to large projects Real projects are rarely sequential

P M d l


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Prototype Model

It is also known as throw away model.

It is developed as per the current available

requirement.

The code for the prototype model is

thrown away; however the experience

gathered from developing the prototype

helps in developing the actual system.


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Linear model

Rapid

Prototype Model


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Requirementsspecification

Architecturaldesign

Detailed

design

Implementationand unit testing

Integrationand testing

Operation andMaintenance

Iterative Enhancement Model


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Evolutionary Process Models

Evolutionary process model resembles iterativeenhancement model. The same phases as defined for the

waterfall model occur here in a cyclical fashion. This model

differs from iterative enhancement model in the sense that

this does not require a useable product at the end of each

cycle. In evolutionary development, requirements are

implemented by category rather than by priority.

This model is useful for projects using new technology that

is not well understood. This is also used for complexprojects where all functionality must be delivered at one

time, but the requirements are unstable or not well

understood at the beginning.


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Evolutionary Development Model

Validation Finalversion

Development Intermediate

versions

Specification Initial

version

Outline

description

Concurrent

activities

Spiral Model


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Spiral Model

Phases of Spiral Model Planning: Determination of objectives,

alternatives and constraints.

Risk Analysis: Analyze alternatives andattempts to indentify and resolve the risks

involved

Development: Product development andtesting product.

Assessment: Customer evaluation

Spiral Model


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Spiral Model



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o Build a rapid prototype

o Give it to user for evaluation & obtain feedback

o Prototype is refined

Requirement

sPlanning

User

Description

Construction Cut over

With active participation of users

p pp p ( )


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Not an appropriate model in the absence of user

participation.

Reusable components are required to reducedevelopment time.

Highly specialized & skilled developers are required

and such developers are not easily available.


Multiple Choice Questions


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1.1 Software is

(a) Superset of programs (b) subset of programs(c) Set of programs (d) none of the above

1.2 Which is NOT the part of operating procedure manuals?

(a) User manuals (b) Operational manuals

(c)Documentation manuals (d) Installation manuals

1.3 Which is NOT a software characteristic?

(a) Software does not wear out (b) Software is flexible

(c) Software is not manufactured (d)Software is always correct

1.4 Product is

(a)Deliverables (b) User expectations(c) Organization's effort in development (d) none of the above

Multiple Choice QuestionsNote: Select most appropriate answer of the following questions:

1.5 To produce a good quality product, process should be

(a) Complex (b)Efficient

(c) Rigorous (d) none of the above

Multiple Choice Questions


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1.6 Which is not a product metric?

(a) Size (b) Reliability

(c)Productivity (d) Functionality

1.7 Which is NOT a process metric?

(a) Productivity (b)Functionality

(c) Quality (d) Efficiency

1.8 Effort is measured in terms of:(a)Person-months (b) Rupees

(c) Persons (d) Months

1.9 UML stands for

(a) Uniform modeling language (b)Unified modeling language

(c) Unit modeling language (d) Universal modeling language

p QNote: Select most appropriate answer of the following questions:

1.10 An independently deliverable piece of functionality providing access to

its services through interface is called

(a) Software measurement (b) Software composition

(c) Software measure (d)Software component


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Thank You

Documents

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