SQM-Unit1 and Unit 2

8/4/2019 SQM-Unit1 and Unit 2

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Software Quality

UNIT - 1


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Introduction

Software Quality measures how well the softwareis designed (Quality of design)and how well thesoftware conforms to the design (Quality ofconformance)

Where,

Quality of design concerned about the specifications,design and requirements of the software

Quality of Conformance concerned with theimplementation of the software


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Introduction

The primary goal of engineering the product isTo improve the quality of the software products

To increase the productivity &Job Satisfaction of theengineers

Quality is transparent when it is present and it canbe easily recognized in its absence

For Ex:

When a car falls into piecesWhen a system fails to perform properly


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Introduction

Note:User Satisfaction issue must also be considered

for Quality

User Satisfaction = Good Quality + Deliveredwithin budget and Schedule + Complaintproduct

Most of the developers feel that software qualitycan be carried out only after the code isgenerated. But it is not true. It can be enforcedeach and every stages of a software process


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Introduction

Note:If a team stresses quality in all engineering

activities,

It reduces the amount of rework

Results in lower costVariation control is the heart of Quality Control

For Ex: consider the various versions of OS, amanufacturer has to minimize the variation /

difference between the predicted resources &actual resourcesused including staff, equipment,and calendar time

Cos of this number of bugs will be minimizedfrom one release to another


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Introduction

Note:SQM is the management Technique that can be

applied to the development of software to favorthe quality

Software Quality comprises ofQuality Control

Quality Assurance

Quality Cost


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Introduction

What is Quality?It is a characteristic or an attribute of something

that must conforms to the design standards

Quality can be a measurable characteristics thatcan be compared to length, color etc.,


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Introduction

Insight about Quality?Quality is Not absolute

Quality is Multidimensional

Subject to constraints

Quality criteria are not independant


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Introduction

What is Quality?The degree of Excellence - OED, 1990

Zero Defects Crosby, 1979

The totality of features and characteristics of aproduct or service that bear on its ability tosatisfy specified needs ISO, 1986

Quality of a product is achieved thro its features &characteristics

So it is associated with the attribute of a product throwhich performance can be achieved


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Introduction

Software Quality?Conformance to explicitly stated functional,

performance requirements & developmentstandards and implicit characteristics that are

expected by all softwares

Department of Defense defined a SQ as thedegree to which the attribute of the softwaresenable it to perform its intended end use


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Introduction

Software Quality2 features of quality software:Conformance to its specificationFitness to its intended purpose


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Introduction

Software QualityWhen compared to other industry, Software

Quality will be problamatic coz

It does not have physical existenceLack of knowledge of clientRapid change rate in both hardware &

softwareHigh expectation of the customer


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Introduction

Views of QualityQuality is a multidimensional construct

It can be considered as a Polyhedron Metaphor

where a quality is represented by a 3-dimensional solid & each face represents adifferent aspects of quality

Polyhedron Metaphor is illustrated as


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Introduction

Views of Quality

Timeliness

Cost CorrectnessFunctionality

Reliability

Maintainability

Functionality

CostTimeliness


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Introduction

Views of Quality Based on different characteristics of a product, it is been

classified into number of views or perspectives

These views may be considered based on external

observers viewing towards a product ex: user, supplier orclient etc.,

These views are used to vary & conflict based on differenttypes of peoples who is viewing the product

Ex: viewing persons Project Manager Business Analyst ProgrammerQuality Auditor

End user Line Manager and Project Sponser


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Introduction

Views of Quality In general, conflicting views are represented between

User and Designer

Designer UserGood Specification What I want

Technically correct Fast Response

Easy to maintain Easy to use help menu

Fast development Exception data &reporting

Well documented Input data once

User managed & Welltrained

Access to all systems

Simple Menu Structure Accurate time


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Introduction

Views of Quality conflicting views are classified into 5 types

1. Transcendent view2. Product based view3. Value based view4. Manufacturing view5. User based view


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Introduction

Views of QualityTranscendent view

Value basedProduct based

Manufacturing user based


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Introduction

Views of Quality1. Transcendent view

This view relates quality to excellence or elegance. In large scale projects, it is expensive to innate high

degree of excellence

2. Product based view Quality Cost i.e., to build high quality in a product

it costs high This type of quality can be added to a product in 2

ways Greater Functionality High Quality Solution thro the use of QMS


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Introduction

Views of Quality3. Value based view

This view depends on what price that the customercan afford

With in the software development, this view can be

used to add the quality to a product with the help ofneeded people, time & tools

4. Manufacturing view This view measures the quality in terms of

conformance to requirements


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Introduction

Views of Quality5. User based view

This view can be summarized as Fitness forpurpose

i.e., the intended functionality for the product must

be facilitated according to the user


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Hierarchical Models of Quality

Hierarchical Model To compare quality in different situations

(quantitatively & qualitatively), it is needed to establisha model of quality in hierarchical structure

Ex: Assessment and Reporting method used in School

Student progress report is prepared under series ofheadings such as Subject name with both qualitative& quantitative assessment

These measures are derived from a examination or aformal test


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Hierarchical Model (Cont)

Subject Teachers

Comments

Term

Grade(A-E)

Exam

Mark (%)

English

Maths

ScienceTamil

Social Science

Total

Traditional Assessment Method


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Hierarchical Model (Cont) Presently, the assessment of a person has become

complicated cos a subject may be broken into differentlevel of skillswhere each of the skills are measuredcollectively to give a more detailed result i.e.,


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Hierarchical Model (Cont)

English

Student

Maths Science Social

Student

Maths English Science Social

Oral Skills Reading Skills Writing CreativeOral Skills Reading Skills Writing Creative

English

Has evolved into


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Hierarchical Model (Cont) Based on different measures of software, its quality can

be depicted as:

Quality factor

Quality criterion

Ex: Maintainability

Quality criterion

Ex: Reliability

Quality criterion

Ex: Usability

Quality Metrics Quality MetricsQuality Metrics

Ex of Metrics: Accuracy, Consistency, Error Toleranceand simplicity


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Hierarchical Models of Quality These models are used to identify the needed quality

criteria's that can be used in improving the resultantquality of the product

Types of quality models

1. McCall Model

2. Boehm Model

3. FURPS Model

4. ISO 9126 Model5. Dromey Model


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Hierarchical Model of McCall Proposed by McCall in 1977. It is also referred as

General Electronics model after McCall

This model is originates from US military developed forUS Air force

This model can be used during the development processby the system developers

In this model, McCall attempts to bridge the gapbetween users & developersby focusing number ofquality factors that reflect both the user views &developer priorities


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Hierarchical Model of McCall

ProductRevision

ProductTransition

Product operations

MaintainabilityFlexibility

Testability

PortabilityReusability

Interoperability

Correctness, Reliability, Efficiency, Integrity, and Usability


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Hierarchical Model of McCall McCall model identifies 3 areas of software work or 3 types of

quality characteristics

1. Product operation

2. Product revision

3. Product Transition

Product Operation It explains the working operation of theproduct that can be learned easily efficiently

Product Revision- It concerned with error correction of the system

- The system may undergo changes

Product Transition This is applicable in distributed

applications & adaptable to new environments


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Hierarchical Model of McCall McCall defines following 11 quality factors:

Usability

Integrity

Efficiency

Correctness

Reliability

Maintainability

Flexibility

Testability

Portability

Reusability

Interoperability

Execution efficiency

Storage efficiency


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Hierarchical Model of McCall McCall identifies 3 areas of software work in a hierarchy

of factors, criteria and metrics

11 factors (To specify) External view of the softwareseen by the users

23 criteria's (To build) Internal view of the softwareseen by developers

Metrics (To control) method of measurement


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Hierarchical Model of Boehm (1978) This model is presented by Barry W Boehm

Boehm model definesset of well defined,differentiated characteristics of software quality where

the quality criteria's are subdivided.

In this first division is named asgeneral utility andthe next one isAs-is utility that is the subtype of firstone.


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Hierarchical Model of Boehm (1978) It is similar to McCalls model where a quality of

software is structured around

Higher levelcharacteristics

Intermediate levelcharacteristics

Primitivecharacteristics


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Hierarchical Model of Boehm (1978) Higher levelcharacteristics it addresses answers for 3

questions:

As-is Utility [How well (easily, reliably, efficiently) can Iuse as-is?]

Maintainability [How easy is it to understand, modify andretest?]

Portability [can I still use it even if I change theenvironment]


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Hierarchical Model of Boehm (1978) Intermediate levelcharacteristics It identifies 7 quality

factors that are expected by the software:

Portability

Reliability

Efficiency

Usability

Testability

Understandability

Flexibility

As-is Utility

Maintainability characteristics


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Hierarchical Model of Boehm (1978) Primitivecharacteristics Provides the foundation for

defining quality metrics


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Device Independence

Self-contained ness

Accuracy

Completeness

Robustness / Integrity

Consistency

Accountability

Device EfficiencyAccessibility

Communicativeness

Self descriptiveness

Structuredness

conciseness

Legibility

Augment ability

Portability

Reliability

Efficiency

Human Engineering

Testability

Understandability

Modifiability

Maintainability

As-is Utility

General Utility


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Summary of McCall & Boehm Models Boehms and McCalls models might appear very similar.

the difference is that:

McCalls modelprimarily focuses on the precisemeasurement of the high-level characteristics As-isutility

Boehms quality model is based on a wider range of

characteristics with an extended and detailed focuson primarily maintainability.


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Comparison of McCall & Boehm Models by QF to QF


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Quality Measurement

Measurement of quality is one of the key problemhighlighted by IT practitioners

Quality measurement is expressed in terms of Metrics thatis a measurable property which is an indicator of one or

more quality criteria that are seeking to measure

Conditions that the quality metric are:

It must be linked to the quality criterion that it seek tomeasure

It must be sensitive to different criterion

It provides determination of the criterion


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Quality Measurement

Measurement technique to a software is similar to thetraditional science methods. But it is more complex

Structuredness is the main factor for the software throwhich quality can be measured.

Well structured code is easy to maintain & adapt which canbe calculated in terms of average length of code modules inthe program

Lines of code

Structuredness modularity ----------------------------

Number of modules


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Quality Measurement

Software Metrics Structuredness is used to predict the maintainability,

reliability & adaptability of the software later in thelifecycle

Classified into 2 types:

Predictive Metrics

Descriptive Metrics


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Quality Measurement

Software Metrics (Cont) Predictive MetricsIt is used to make predictions about

the software later in the life cycle

Descriptive MetricsIt describes the state of the

software at the time of the measurement

For Ex: reliability metricmight be based upon the

number of system crashes during the given period


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Quality Measurement

Software Metrics (Cont) McCall & Boehm have defined many number of

approaches to find metrics

McCalls approach is quantitative where structurednessof a software can be measured by

n01Structuredness = -----------

ntot

Where, n01 = number of modules having one or zero exit

points

ntot = total number of modules

This metric valuelies between 0 to 1


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Quality Measurement

Software Metrics (Cont) Using Boehm concept, structuredness can be measured

by addressing the answer for following questions:

Have the rules for transfering control between

modules been followed? (Y/N) Are modules are limited in size? (Y/N)

Do all modules have one exit point? (Y/N)

Do all modules have only one entry point? (Y/N)


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Quality Measurement

Software Metrics (Cont) What makes a good Metric?

After McCall & Boehm concepts, a scientist Wattshad publishes an analysis of metrics. And hesuggests 7 quality criterias of good software metric

Objectivity

Reliability

Validity

Standardization

Comparability

Economy

Usefulness


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Quality Measurement

Software Metrics (Cont) Metric Ranking

Wattshad cited /quoted 40 metrics from thesoftware engineering

Among these 40 metrics, 3 quarters of 40 metrics areconcerned with 2 criteria namelyreliability &maintainability

4 criterias are not metricated

3 criterias have only one metric


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Quality Measurement

Software Metrics (Cont) Wattshad ranked following criterias based on no.

of metrics

Quality Criteria Number of metrics cited

Maintainability 18

Reliability 12

Usability 4

Correctness 3

Integrity 1

Expandability 1

Portability 1

Efficiency 0

Adaptability 0

Interoperability 0

Reusability 0


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Quality Measurement

Software Metrics Ranking The set of metrics quoted is based on 7 distinct

measurable properties:

1. Readability

2. Error Prediction

3. Error Detection

4. Complexity

5. MTTF (Mean Time To Failure)

6. Modularity

7. Testability


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Quality Measurement

Software Metrics Ranking (Cont) Relationship b/w Quality Criteria & Measurable

properties are:

Readability

Error Prediction

Error Detection

Complexity

MTTF

Modularity

Testability

Usability

Integration

Correctness

Reliability

Maintainability

Expandability

Portability

Others

Measurable Properties Quality Criteria


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Quality Measurement

Software Metrics Ranking (Cont)1. Readability as a measure of usability:

This measure is applied in documentation to asseshow such documentation assist in the usability of apiece of a software

2 methods:

a) Flesch-Kincaid readability index forms

b) Fog Index

First method works at a syllable level & calculatedusing the formulae:

Grade Level = 0.39a + b - c

a = no. of words in the sentenceb=mean no. of syllables per 100

words

c = 15.59


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Quality Measurement

Software Metrics Ranking (Cont)1. Readability as a measure of usability:

Fog index method:

Fog Index = 0.4a + b

a = no. of words in the sentenceb= percentage of words with more than 2 syllables


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Quality Measurement

Software Metrics Ranking (Cont)2. Readability as a measure of Maintainability:

Readability of source code can be done in terms of

Statement lines

Average length of variable names

Total number of program branches


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Quality Measurement

Software Metrics Ranking (Cont)3. Error Prediction as a measure of Correctness:

With reference to the quote of Halstead, usingBasic parameters such as number of operators &operands one can predict

Number of errors found during validation Total number of errors found during

development


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Quality Measurement

Software Metrics Ranking (Cont)4. Error Detection as a measure of Correctness:

Total number of errors which are not detected has tobe predicted usingRemus, Zilles model (says no. of

detected errors) and error detection efficiency

Number of defect Program length and defectremoval rate


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Quality Measurement

Software Metrics Ranking (Cont)5. MTTF as a measure of Reliability:

MTTF is given by

tTOT

MTTF = ---------

Rt

tTOT = Total time periodRt = number of failures in tTOT


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Quality Measurement

Software Metrics Ranking (Cont)5. MTTF as a measure of Reliability:

MTTF can be assessed by measurement, estimationor prediction

Reliability can be calculated using the measures

Current MTTF (tF)

Length of the operation phase (tOP)

tOPReliability, R1 = exp ---------

tF


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Quality Measurement

Software Metrics Ranking (Cont)6. Complexity as a measure of Reliability:

If a Complexity of software gets increasesthen thereliability will decreases

For Ex: Logical complexity of the software can be

measured by the concept of CyclomaticComplexity

7. Complexity as a measure of Maintainability:

If a Complexity of software gets increasesthen themaintainability will get affected


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Quality Measurement

Software Metrics Ranking (Cont)8. Modularity as the measure of Maintainability:

If a modularity increases in the software then theMaintainability of software will also increases

9. Testability as the measure of Maintainability:

Ease & effective testing will have a positive impacton a product

The effectiveness of testing will be measured by theconcept raised by Woodward


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Quality Measurement

Problems on Software Metrics The overall measure of quality can be calculated by

following measures:

1. Simple Scoring

2. Weighted Scoring

3. Phased weighting factor method

4. The Kepner-Tregoe Method

5. The Cologne combination method


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Quality Measurement

Problems on Software Metrics1. Simple Scoring

In this method, each quality criteria is allocated witha score

Overall quality is given by the mean of individualscores

Sum of each Metric Score

Simple Score = ---------------------------------------------------Total number of Metric scores


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Quality Measurement

Problems on Software Metrics1. Example: Simple Scoring

Quality Criteria MetricValue

Usability 0.7Security 0.6

Efficiency 0.4

Correctness 0.8

Reliability 0.6Maintainability 0.6

Adaptability 0.7

Expandability 0.7

Simple Score = ?


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Quality Measurement

Problems on Software Metrics2. Weighted Scoring

In this method, each Quality Criteria can beweighted based on its importance

Each quality criterion is evaluated to produce a score

between 0 & 1

Sum of Product of each Metric

Weighted Score = -------------------------------------------

Sum of each Metric weight

Where, Product = Value of each Metric Score X

weight of each Metric score


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Quality Measurement

Problems on Software Metrics2. Problem 1: Weighted Scoring

Quality Criteria MetricValue

Weight

Usability 0.7 0.5Security 0.6 0.2

Efficiency 0.4 0.3

Correctness 0.8 0.5

Reliability 0.6 0.4Maintainability 0.6 0.4

Adaptability 0.7 0.1

Expandability 0.7 0.1

Weighted Score = ?


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Quality Measurement

Problems on Software Metrics3. Phased weighting factor method

It is an extension of weighted scoring

Here weighting is assigned to a group of

characteristicsbased on work areas defined byMcCall

In this method, 2 work areas[Product Operation &Product Transition]are focused to produce qualitywhere each area will be assumed with additionalweightage of characteristics


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Quality Measurement


3 measures has to be calculated:

Product Operation Weighted Mean (POWM)

Product Transition Weighted Mean (PTWM)

Overall Measure by PWF method

Sum of Product of each PO quality criteria

POWM = -----------------------------------------------------------

Sum of weight of each PO quality criteria


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Quality Measurement


Sum of Product of each PT quality criteria

PTWM = --------------------------------------------------------

Sum of weight of each PT quality criteria

PWF is the additional weighting factor that will be

assumed for the calculation. For Ex: PWF for Product Operations = 2/3

PWF for Product Transition = 1/3

Overall Measure by PWF = ((2/3) X POWM) + ((1/3) X PTWM)


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Quality Measurement

Problems on Software Metrics3. Problem 2: Phased Weighted Scoring

Group Quality Criteria MetricValue

Weight PWF

ProductOperation

Usability 0.7 0.5

2/3

Security 0.6 0.2

Efficiency 0.4 0.3

Correctness 0.8 0.5

Reliability 0.6 0.4

ProductTransition

Maintainability 0.6 0.4

1/3Adaptability 0.7 0.1


POWM = ? ; PTWM = ?; Overall Measure = ?


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Quality Measurement

Problems on Software Metrics3. The Kepner-Tregoe Method

In this method, quality criteria is divided into 2 parts

Essential minimum value will be specified for eachcriteria

desirable

4. The Cologne combination method

This method facilitates comparative evaluation

Each product will be ranked based on chosen criteria


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Quality Measurement

Problems on Software Metrics Problem 3: Using the following data & the PWF method,

calculate the following: POWM, PTWM and overallmeasure of the product

Group Quality Criteria Metric

Value

Weight PWF

ProductOperation

Usability 0.7 0.5

2/3

Security 0.5 0.5

Efficiency 0.6 0.2

Correctness 0.7 0.5Reliability 0.4 0.4

ProductTransition

Maintainability 0.8 0.4

1/3Adaptability 0.7 0.1



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Quality Measurement

Polarity Profiling In this scheme, Quality of a product is specified in the

ranges from -3 to +3

Comparison analysis is made between required quality

& the actual quality achieved

4 quality criterias have been focused for this methodwhich are namely

Efficiency

Reliability

Maintainability

Adaptability

These criterias would beUsefulto analyze usersatisfaction of the product


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Quality Measurement

Polarity Profiling (Cont) When a user complaints about the quality, software

engineer has to improve the product in these areas

Polarity Profiling is the graphical profiles

representation of quality criterias to asses thesatisfaction / expectation of the user

Using this scheme, an engineer can asses the level ofuser happiness where by user expectations & the

developer tension can be minimized


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Quality Measurement

Example: Polarity Profiling (Cont)

Unusable

InsecureInefficientIncorrectUnreliableUnmaintainable

Not Adaptable

-3 -2 -1 0 1 2 3

-3 -2 -1 0 1 2 3

Usable

SecureEfficientCorrectReliableMaintainable

Adaptable

Where, = Achieved quality &= required quality

Reliability & efficiency not up to the


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Polarity Profiling (Cont)

Consider the following situation


Unusable


Not Adaptable

-3 -2 -1 0 1 2 3

-3 -2 -1 0 1 2 3

Usable


Adaptable

Reliability & efficiency not up to thereqd. std. where as adaptability& maintainability appears to be

beyond the levelUsers wont get Happy

Reliability & efficiency reaches the


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Polarity Profiling (Cont) Consider the following situation


-3 -2 -1 0 1 2 3

Unusable


Not Adaptable

-3 -2 -1 0 1 2 3

Usable


Adaptable

Reliability & efficiency reaches thereqd. std. where as adaptability

& maintainability also appears to bereaches the level

Users will be Happy


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Polarity Profiling (Cont) Problem

Quality Criteria ActualQuality

RequiredQuality

Usability 0.3 0.7Security 0.5 0.7

Efficiency 0.3 0.6

Correctness 0.9 0.9

Reliability 0.9 0.9Maintainability 0.4 0.8

Adaptability 0.4 0.8

Discuss the possibilities of User Satisfaction in this module?


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Quality Measurements

Gilbs Approach It is an iterative approach aiming to converge towards

clear & measurable multidimensional objectives

This approach makes use the concept of McCall &

Boehm models

For each stage, a partial product can be viewed with userwhere a product will be evaluated to identify whether itmeets the needs of user. If it does not satisfy errors has

to be identified & cleared out during the next iterationuntil a product gets satisfied by the user.


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Gilbs Approach 5 problem areas highlighted

Simple fact that the method is different

Need of training & re-training and associated costs

Need of effective management

Need to measure progress towards the ultimate goal

Picking up errors


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Gilbs Approach With reference to Gilbs approach, product quality can

be measured in terms ofQuality Template

It models quality in terms ofQuality attributes&

Resource attributes. This is because quality of a productcan be constrained by the available resources


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Gilbs Approach

Quality Template can be pictured as:

WorkabilityAvailability

Adaptability

Usability

Other Qualities

PeopleTime

Money

Tools

Other Resources

Qualities Resources


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Gilbs Approach Quality Attributes

1) Workability

2) Availability

3) Adaptability

4) Usability


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Gilbs Approach: Quality Attributes & its sub-attributes

Workability

Process Capacity

Storage Capacity

Responsiveness

Availability

Reliability

Maintainability

Integrity

Adaptability

Improvability

Extendability

Portability

Usability

Entry Level Requirements

Learning level requirements

Handling ability

Likability


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Gilbs Approach: Quality Attributes1) Workability

It is defined as the ability of the system to do work(i.e., transaction processing)

Divided into sub-attributes of: Process capacity It is the ability of the system to

process transactions with in a given unit of time

Storage capacity It is the ability of the system tostore information

Responsiveness It is a measure of the responseto a single event


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Gilbs Approach: Quality Attributes2) Availability

It is the ability of the system to be used with theproportion of elapsed time

Classified into Sub attributes of:a) Reliability

b) Maintainability

c) Integrity


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a) Reliability

It is the ability of the system that should not failfrom its operating environment under any

circumstances

It is the degree to which the system does what itshould to do.

Coz purpose of a system is different & thepurpose of parts of a system will be different. Sothe assessment of reliability will also vary


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a) Reliability

Based on the analysis of Dickson, Gilbs havesuggested that reliability can be assessed in terms

of Fidelity

Veracity

Viability

For both Logicware (code)and Dataware (data files)


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Gilbs Approach: Quality Attributes Dicksons classification of Reliability

Logicware

Fidelity Concerned with the accuracy of algorithmimplementation

Veracity Concerned with the representation of real

world be an algorithm

Viability Is the extent to which an algorithm meets itsspecification in terms of performance &requirements

Dataware

Fidelity Says how accurately an idea is represented by

the data within a application

Veracity How well the data matches with the world

Viability How well the required data fits the designconstraints


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b) Maintainability

It is the effort required to locate & fix a fault in theprogram within its operating environment

It is the process of fault handling

Sub-attributes of Maintainability are:

Problem recognition Inspection TimeAdministrative Delay Active Correction

Tool Collection Testing

Problem analysis Test Evaluation

Correction Recovery


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c) Integrity

It is the protection of the program fromunauthorized access

It is a measure of a system to remain intact underthreat

Integrity may affects availability

So. A system with poor integrity is likely to beunavailable for much time


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Gilbs Approach: Quality Attributes3) Adaptability

Classified into sub-attributes of:

Improvability It is the time taken to makeminor changes to the system

Extendability It is the ease of adding newfunctionality to a system

Portability It is the east of moving a systemfrom one environment to another


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Quality Measurements Gilbs Approach: Quality Attributes

4) Usability

It is the ability of the system that should facilitate the easeof use & effectiveness of a system

Classified into sub-attributes of:

Handling ability It is a measure that says how wellproductivity can be proceeded after the error is detected

Entry level requirements are human capabilities such asintelligence level, language proficiency

Learning level requirements are resources such as timeneeded to reach the performance of the system

Likability It says how well people like the system


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Gilbs Approach: Resource Attributes

People

Time

Money

Tools

Other Resources


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Gilbs Approach: Resource Attributes Time Resource

2 types

Calendar time to delivery

Time taken by the system to carry out the task

People Resource

Measured in terms of Man-years

But the availability of People for the particular

development is critical Ex: can not utilize PASCAL programmers for C

programming


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Quality Measurements Gilbs Approach: Resource Attributes

Money Resources

Concerned with both development & maintenancecosts

In general, 80% of cost would be spent to

maintenance for quality improvement

Tool Resources

It comprises all physical resources


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For continuous improvements, these resources will beconsidered as constraints to a product

People

TimeMoney

Tools


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Gilbs have defined some measures to quantify thoseattributes. And these can be measured in terms of unitsper time

For ex: Transactions per second

Records per minute

Bytes per line

Bits per node per second


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Workability

ProcessCapacity

Units per time Transactions per sec.

StorageCapacity

Units stored Bytes per second

Responsiveness Actions per time Response time

Attribute Sub-attribute General measure Example

l


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Quality Measurements GQM Model

GQM, the acronym for "Goal, Question, Metric

It is an approach to Software Metrics

It was developed by Victor Basili of the University ofMaryland & the Software Engineering Laboratory at theNASA Goddard Space Flight Center

li


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GQM defines a measurement model on three levels:

Conceptual level (goal)

A goal is defined for an object for a variety ofreasons, with respect to various models ofquality, from various points of view and relative

to a particular environment. Operational level (question)

A set of questions is used to define models of theobject of study and then focuses on that object tocharacterize the assessment or achievement of a

specific goal. Quantitative level (metric)

A set of metrics, based on the models, isassociated with every question in order to answerit in a measurable way.

Q li


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GQM templates are a structured way of specifying goals

Field Examples

Object of study pair programming, static analysis tool

Purpose characterize, understand, evaluate,predict

Focus programmer effort, program reliability

stakeholder developer, customer, manager

Documents

SQM-Unit1 and Unit 2