software quality features models

8/2/2019 Software Quality Features Models

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Unit 4

Software Quality:Features and Models

Software Quality


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Calidad del Software

Quality models are used to build betterproducts or services and to assure their

quality.Software quality models are used to

evaluate a software taking into accountcriteria for satisfying:

Developers needsMaintainers needsClients that buy the softwareEnd users.

Quality models


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Quality models FCM (Factors/Criteria/Metrics) McCall (1977) Boehms Model (1978) GQM Paradigm (Goal-Question-Metric) (1988) Gilbs Model(1988) Framework ISO 9126 (1991) CMM (Capability Maturity Model) (1993) SPICE(Software Process Improvement and

Capability determination) (1999) CMMi (Capability Maturity Model Integration)

(2000)


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McCalls modelFactors/Criteria/Metrics (McCall)

Each determinant factor of quality is dividedinto several properties or criteria, whichdetermine quality.

Criteria are evaluated by means of metrics.


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The model divides quality concept into threemain perspectives for characterizing the

quality attributes of a software product:

Product Operation (basic operationalcharacteristic).

Product Revision (ability to chance)Product Transition (adaptability to newenvironments).

McCalls model


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McCalls model

Portability. Reusability. Interoperability.

AdaptabilityProduct Transition

Maintainability. Flexibility. Testability.

Ability to change.Product Revision

Correctness. Reliability. Efficiency, system resource usage. Integrity. Usability.

Basic Operational

Characteristic.

Product Operations

FactorsPoint of view


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McCalls model

Completeness Consistency Traceability

Correctness, the

functionality matches the

specification.

Access control Easiness of be audited Security

Integrity, protection from

unauthorized access

Easiness of be operated Easiness of communication Easiness of be learnt Training

Usability, ease of use

CriteriaFactors


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McCalls model

Running efficiency Storing efficiencyEfficiency, system resource(including cpu, disk,

memory, network) usage

Precision Consistency Faults tolerance Modularity Simplicity accuracy

Reliability, the extent to

which the system fails

CriteriaFactores


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McCalls model

Self description Capability of expansion Generality

Modularity Simplicity Self description Instrumentation

Modularity Simplicity Consistency Conciseness Self description

Flexibility, the ability to make

changes required as dictated

by the business.

Testability, the ability to

Validate the software

requirements.

Maintainability, the ability to

find and fix a defect

CriteriaFactors


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McCalls model

Self description Modularity Independence

Portability, the ability totransfer the software from

one environment to

another.

Modularity Communications compatibility Data compatibility Data standarization

Interoperability, the extent,

or ease, to which software

components work together.

Self description Generality Modularity Software independence Hardware independence

Reusability, the ease of using

existing software components

in a different context

CriteriaFactors


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It is a hierarchical model and it is focused in the

final product.

Boehms model


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GQM Paradigm (Goal-Question-Metric) GQM is a top-down approach to establish a goal-

driven measurement system for softwaredevelopment, in that the team starts withorganizational goals, defines measurement goals,poses questions to address the goals, andidentifies metrics that provide answers to the

questions.

GQM paradigm


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It is based on a clear definition of the goals. Themodel provides a structure to achieve crucial goals ofthe project. GQM defines a measurement model on

three levelsConceptual level (Goal) : a goal is defined perentity.

Operational level (Question): a set of question isrefined, in order to identify the measuring object.Quantitative level (Metric): a set of metric isassociated to each one of the questions.

GQM paradigm


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GQM paradigm

There are three stages:

List main goal for project development andmaintenance.

Per each one of the objectives to determinequestions to be answered in order to know if objectiveis going to be achieved.

To decide what to measure in order to answerquestions in an appropriate way. Individual measures

are correlated to be used in the context of the whole

project.


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GQM paradigm

Questions:

Objective: To evaluate standard of codification effectiveness

Whos usingthe standard?

Codemakerspercentage

using:

standard,language

Codemakerproductivity?

Codemakersexperience

on: standard,

language,environment,

Code quality?

Code quantity Errors



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Gilbs Model

This model appears in 1988. The modelincludes final software user expectations by

the first time in history.It presents quality attributes definition inwhich user is really interested in aquantitative way.

The model also defines the quality levelneeded to satisfy the final user per each oneof the attributes.


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The model proposes characteristic such as: correctness,integrity, maintainability, and usability. They can be measuredby several detailed metrics or sub-characteristics.

Each one of them must specify the following concepts:Name and characteristic definition.Scale or measuring units.Data collection or proof.Predicted value.Optimal value.Value at current system.Comments.

Gilbs Model


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ISO 9126

In 1991, the International Organization forStandardization introduced a standard named ISO/IEC 9126 (1991): Software product evaluation -Quality characteristics and guidelines for their use.This standard aimed to define a quality model forsoftware and a set of guidelines for measuring thecharacteristics associated with it.

It is known by: Software Product Evaluation:Quality Characteristics and Guidelines for theirUse.


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ISO 9126-1

Revised in 2001, ISO/IEC 9126-1 recognizes threeaspects of software quality:

Quality in use

External qualityInternal quality


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ISO 9126-1:2001

External and

internal quality


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QUALITY IN USE

Quality in use is the user's view of the quality of

the software product when it is used in a

specific environment and a specific context of

use. It measures the extent to which users can

achieve their goals in a particular environment,rather than measuring the properties of the

software itself. (ISO/IEC, 2001a)

ISO 9126-1:2001


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ISO 9126-1:2001

Adapted from (ISO/IEC, 2001a)


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Second generation of quality standards ISO/IEC CD

25010:2007 (Software engineering-Software Product

Quality Requirements and Evaluation (SQuaRE)-qualitymodel).

In this case, two important sub-factor security and

interoperability- have became factors in the newstandard.

This model is also known as External and Internal

Quality.


(SQuaRE)-Quality model


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External and Internal Quality

Confidentiality Integrity Non-repudiation

Accountability Authenticity Compliance

Security

Appropriateness Accuracy Compliance

Functionability


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Maturity Fault tolerance Recoverability Compliance

Reliability

OSI compatibility SW Compatibility Data compatibility Traceability Compliance

Interoperability



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Efficiency

Understandability Learn-ability Operability Attractiveness Compliance

Usability

Time behavior Resource behavior Compliance


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Adaptability Install-ability Co-existence Replace-ability Compliance

Portability

Analyzability Change-ability Stability Testability Compliance

Maintainability


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SQuaRE - ISO/IEC CD 25010 also re-definesquality in use adding two new factors.

Quality in use is, now, measured in the

operational ambient, it depends on software,

hardware, users, etc.


Quality in use


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Quality in use

Types of users in use Tasks of use Environment of use Context conformity in use

Context in use

Effectiveness in use Productiveness in use Satisfaction in use Compliance in use

Usability in use


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Quality in use

Operator health and safety Public health and safety Environmental harm in use Commercial damage in use Compliance

Safety in use


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Quality in use

Risk for operator in use. Risk for software in use

corruption. Commercial risk in use. Risk compliance in use. Security in use. compliance.

Security in use


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Learn-abililty in use Flexibility in use Accessibility in use Compliance

Adaptability in use

Quality in use


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To reach Quality in use depend on reachingexternal quality, which is also dependent on

reaching internal quality.Measures to be done must assure to get the

three necessary quality levels.


Quality in use


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Having the opportunity to correct misalignedprocesses.

To classify companies.To achieve competitiveness.To certify international competitiveness.To assure continuous improvement.


Advantages of using

Model


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To increase productivity. To reduce costs. To ensure the satisfaction of internal and externalcustomers. To generate a culture within the organization. To have criteria and indicators for measuring the

strengths and weaknesses of the organization tomake improvements.

Advantages of using

Model


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Calidad del Software36

Conceptual models

TYPES OF CONCEPTUAL MODELS

TRADITIONAL CONCEPTUAL MODELS: LikeEntity-Relationship Model (ERM).

OBJECT ORIENTED CONCEPTUAL MODELS:They are used not only for data

representation, but also System Informationfunctionality and behavior.

software quality features models

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