2 - software processes

7/30/2019 2 - Software Processes

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Reference: Software Engineering, by IanSommerville, 9th edition, Chapter 2


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Objectives

To introduce the idea of software process acoherent set of activities for softwareproduction.

Understand the concepts of software

processes To describe various generic software process

models and their pros and cons

Know about the fundamental process

activities Understand why processes should cope with

changes in requirements and design


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Software ProcessDefinition:

the set of related activities that leads to

the production of a software product. These activities may involve

developing software from scratch.

Evolution of an existing software

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Activities in Software Process

Software Specification

what the system should do and its development constraints,

Software Design and Implementation

production of the software system

Software Verification

checking that the software meets the requirements,

Software Validation

checking that the software does what the customer wants,

Software Evolution

changing the software in response to changing customerdemands.

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Software Life Cycle The phases necessary to develop and maintain a

software system. These phases include:

Requirements (Specification)

Design

Implementation (Coding)

Testing (Validation)

Maintenance (Evolution)

Asoftware process model is an abstractrepresentation of how these phases can beaddressed.


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Requirements

The process of establishing

what services are required of the system

the constraints on the systemsoperation and development

The what of the software life cycle


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A Generic Requirements Process

Feasibilitystudy

Requirementselicitation and

analysisRequirementsspecification

Requirementsvalidation

Feasibilityreport

Systemmodels

User and system

requirements

Requirements

document


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Design

The process of converting the system specification(requirements) into a software structure that realizesthat specification

The how of the software life cycle


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A Generic Software Design Process


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Implementation

Implementation is the process of converting asystem specification into an executable system.

Translating a design into a program and removingerrors from that program

Programming is a personal activity - there is nogeneric programming process.

Programmers carry out some program testing todiscover faults in the program and remove thesefaults in the debugging process.

The activities of design and implementation areclosely related and may be interleaved.


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Testing

Verification and validation is intended to show thata system conforms to its specification and meetsthe requirements of the system customer.

Involves checking and review processes and system

testing System testing involves executing the system with

test cases that are derived from the specification ofthe real data to be processed by the system.


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A Generic Testing Process

Sub-systemtesting

Moduletesting

Unittesting

Systemtesting

Acceptance

testing

Componenttesting

Integration testing Usertesting


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V-Model of Test PlanningRequirementsspecification

Systemspecification

Systemdesign

Detaileddesign

Module andunit codeand tess

Sub-systemintegrationtest plan

Systemintegrationtest plan

Acceptancetest plan

Service Acceptancetest

Systemintegration test

Sub-systemintegrat ion test


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System Maintenance Software is inherently flexible and can change (as

opposed to hardware).

In the past, there has been a demarcation betweendevelopment and evolution (maintenance). This is

increasingly irrelevant as fewer and fewer systems arecompletely new.

Software engineering should be thought of as anevolutionary process where software is continually

changed over its lifetime in response to customerneeds.


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Summary In every software project, large or small, there are five

phases that will be involved: Requirements gathering/analysis

Design Implementation /coding

Testing

Maintenance

However, there is no rule of thumb that these phasesmust be followed systematically. In most projects,developers do as they find appropriate depending onthe type of project.


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END

Next: We will look at Software Process Models

2 - software processes

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