MELJUN CORTES Software Engineering

© QAI India Limited. All rights reserved.

WHAT IS SOFTWARE

ENGINEERING?

INDIA | USA | UK | CHINA | MALAYSIA | SINGAPORE

A presentation by

QAI

What is

Software Engineering?

3

What is Software?

• Program

• Data

• Document

4

Types of Software

• Application software - Application software is used to provide

services to customers and run businesses more efficiently.

Examples: accounting system, a management information

system (MIS), and an enterprise resource planning (ERP)

system.

• System software - System software is used to operate and

maintain a computer system. It enables customers to use the

computer resources directly and through other software.

Examples: operating systems, compilers, and system utilities.

What is embedded software?

5

Engineering Principles

• Fundamental engineering principles:

– Understanding the problem

– Communicating with the customer

– Defined methods for designing

– Best practices for implementing the solution

– Good strategy and tactics for testing

6

Engineering and Software Engineering

• Engineering is the systematic application of scientific

knowledge in creating and building cost-effective solutions to

practical problems in the service of mankind.

• Software engineering is that form of engineering that applies

the principles of computer science and mathematics to

achieving cost-effective solutions to software problems.

1990 SEI Report on Undergraduate Software Engineering Education

( CMU/SEI-90-TR-003 )

7

What is Software Engineering

• The term “software engineering” was first coined at

the 1968 NATO conference where Mr. Bauer was a

principle organizer

• The term “Software Engineering” has been around

for 34 years!

8

Why Software Engineering?

• A 1994 study by the Standash Group of 8,380

projects in the government and private sectors in

the U.S. showed that:

- 31% of software projects are cancelled before they are

completed.

- 53% of those are completed cost an average of 189% of their

original estimates.

- of those 53%, only 42% have their original set of proposed

features and functions.

- only 9% of the projects were completed on time and within

budget.

9

Software Engineering Layers

• Process: A framework that helps the project manager control

project management and engineering activities

• Methods: The technical activities required for the creation of

work products

• Tools: The automated assistance for processes and methods

14

Software Engineering

The application of a systematic, disciplined, quantifiable

approach to the development, operation, and maintenance of

software :

The application of engineering to software

• Objectives - to ensure that

– software delivers functionality, features

– project is completed on time

– project is completed within budget

– software is manageable

– software is changeable and long living

– system is maintainable by a developer who is not part of the original

design team

15

Scope of Software Engineering

Processes for development, e.g.,

- contract

- concept

- requirements

- design

- coding

- testing

- change-over

- maintenance

Supporting processes, e.g.,

- project management

- quality assurance

- configuration management

- training

- measurement / metrics

16

Software Life Cycle

• The period of time that begins when a software

product is conceived and ends when the software is

no longer available for use

– phases overlap, are performed iteratively, etc.

– different approaches possible

– another common term - SDLC

• Software life cycle models are also called software

engineering paradigms

17

Sample Software Life Cycle

Concept Exploration

Requirements Analysis

Design

Coding

Test

Installation

Operation/ Maintenance

Retirement

18

Lifecycle Stages

• Analysis

• Design

• Coding/ Development

• Testing

• Implementation

19

Software Requirements

• A consolidated set of requirements explaining the

business needs of the customer

• Translation of the customer requirements to the

requirements of the software to be built

• Important concepts

– Technical requirements

– Non technical requirements

– Functional requirements

– Non Functional requirements

– Scope of Work as an input

– Acceptance criteria

20

Requirements Engineering

• Requirements Definition

– Elicitation

– Analysis or Modeling

– Documentation

– Validation

• Requirements Management

– Change Control

– Requirements traceability

21

Software Design

• A representation of software created to facilitate analysis,

planning, implementation and decision making

• The software design description is used as a medium for

communicating software design information, and may be

thought of as a blueprint of the system

• Often described as :

– high level (system design, global design, interfaces)

– low level (program / component level)

• Format, contents depend on type of application, objective

and audience

22

Coding

• Expressing a design (implementing a design) in a programming

language based on program specifications

• The main visible work

• Also called programming or construction or development phase

23

Testing

• Checking whether the software product meets

requirements

• The purpose of testing is to uncover as many

problems as possible

• If coder and tester are same, testing may be biased

24

User Acceptance

• Acceptance criteria forms the basis of acceptance of

the product / deliverable

– Criteria to be frozen early

– to be agreed between the supplier and customer

– E.g.,

• No defects in core functionalities

• Performance criteria within a tolerance of + and – 2 %

• No interoperability issues

• The user may do an acceptance testing before

accepting the system

25

Installation and Change over

• Moving the system to the customer site

• User training

• Parallel run

• Installation manual / instructions

• Environment set up

26

Operations and Maintenance

• The “real purpose” of the system

• The largest phase

• Changes required to systems for various reasons -

problems to be fixed, new requirements, changes in

policies, statutory laws, etc.

• Often treated as a separate project

27

Software Engineering SDLC

• Software Development Life Cycles

– Classic life cycle

• a sequential paradigm

– Prototyping

• a modeling paradigm

– Evolutionary models like

• Incremental

• Spiral, etc.

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Core Activities & Role

Core Activities Role

Business Requirement Business Analyst

Software Requirement System Analyst

Design Tech Lead/Architect

Coding Developer

Testing Testing Engineer

Deployment Developers

29

Supporting Activities and role

Supporting Activities Role

Project Management Project Manager

Project Leader

Senior Management

Software Configuration

Management

Configuration Controller

Software Configuration Control

Board

Quality Assurance SQA Analyst

Auditor

© QAI India Limited. All rights reserved.

INDIA

USA

UK

CHINA

MALAYSIA

SINGAPORE

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