LOGO Evaluating Quality-in-Use Using Bayesian Networks M.A. Moraga 1, M.F. Bertoa 2, M.C. Morcillo...

Evaluating Quality-in-Use Using Bayesian Networks

M.A. Moraga1, M.F. Bertoa2, M.C. Morcillo2, C. Calero1, A. Vallecillo2

1Universidad de Castilla-La Mancha 2Universidad de Málaga

(Spain)

Paphos, Cyprus - July 8th, 2008 LOGO

Contents

Introduction1

ISO/IEC 91262

Bayesian Belief Networks3

BNs for evaluating QiU4

Conclusions5

Introduction. The ISO approach

Assessing the quality of a software product is, in general, a complex and difficult task.

ISO/IEC 9126 proposes three levels of quality: Internal quality uses a “white box” view of software products External quality uses a “black box” view Quality in use (QiU) is the end-user viewpoint when the

software product is used in its working environment

ISO/IEC 9126

Quality

Efficiency

Maintainability

Portability

Functionality

Reliability

Usability

Efficiency

Maintainability

Portability

Functionality

Reliability

UsabilityQiU

Intern

Extern

Productivity

Safety

Satisfaction

Effectiveness

ISO current approach is questionable

Most efforts so far have been put on evaluating the internal and external quality

… based on the assumption that a good external quality would guarantee a good quality-in-use (QiU)

But we all know that quality does not work that way!

The QiU should be the driving force!

Reasons to challenge the traditional approach

1 Not all the external quality characteristics of a software product have the same influence on its QiU

2 The direct dependency between the EQ and the QiU, forces to over-specify some of the product aspects (which are non critical for the end user), for the sake of ensuring a certain level of QiU. Unnecessarily increasing costs and development efforts, without a

direct effect on the advantages that the end-user perceives

3 Users normally tend to perceive as equally important all the external quality characteristics of a software product when asked about them in the abstract However, when the context-of-use of a soft-ware product is fixed, users are

able to tell apart the product characteristics that really matter (from their point view), from those that are desirable, but not critical

Our position in this paper

We change the focus of the quality assessment concentrating on the QiU as the driving factor for designing a

software product, or for selecting the product that better fits a user’s needs

We propose a “backwards” analysis of the relationship between the external quality and the QiU

The analysis tries to determine the external quality sub-characteristics that are really relevant to ensure the required level of quality in a given context of use in order to avoid superfluous costs or irrelevant features – which

may unnecessarily in-crease the final price of the product

We propose Bayesian Belief Networks to model such relationships, and propose a method to build them for different contexts of use.

Contents

Introduction1

ISO/IEC 91262

Conclusions5

Bayesian Belief Networks

A BN is a directed acyclic graph, whose nodes are the uncertain variables and the edges are the casual or influential links between variables.

The different relationships between the characteristics and sub-characteristics of the external quality and the QiU

Using BNs We can model

The degree of dependence or influence between them

An example of a Bayesian Network

[Taken from Fenton and Neil “Software Metrics Roadmap”]

An example of a Bayesian Network

[Taken from Fenton and Neil “Software Metrics Roadmap”]

Bayesian Belief Networks

Make inferences about the values of the variables

Define the conditional probability tables

Define the structure

Train the BN through a set of controlled experiments

Contents

Introduction1

ISO/IEC 91262

Conclusions5

BNs for evaluating QiU

HYPOTHESIS

EQ has influence on the QiU and this influence can be modelled and studied through a BN

We can conduct backwards analysis on the required level of EQ to ensure a given level of QiU

3) Link2)

BNs for evaluating QiU1st Approach Study the relationships between the different characteristics, identifying

the EQ characteristics that have a significant influence on the QiU characteristics.

Quality in Use

Safety Satisfaction Productivity Effectiveness

ExternalQuality

Functionality X X X X

Reliability X X X

Usability X X

Efficiency X X

Portability X

Maintainability X

BNs for evaluating QiU1st Approach BN

BNs for evaluating QiU1st Approach Probability tables:

3 categories (IEEE Std. 1061):Acceptable, Marginal and Unacceptable The tables of the upper level nodes have a single entry with the evaluation of

the external quality sub-characteristics (opinion of experts). The probability tables of the nodes in the next level have been defined taking

into account the degree of influence that each one has on the corresponding QiU characteristic.

BNs for evaluating QiU1st Approach

BNs for evaluating QiU1st Approach Problem: all sub-characteristics of an external quality characteristic

have the same influence on all related QiU characteristics

Is Suitability as “important” for Safety as for Satisfaction? The answer is, of course, No.

2nd Approach

BNs for evaluating QiU2nd Approach Define relationships between EQ sub-

characteristics and QiU characteristics

BNs for evaluating QiU2nd Approach BN

BNs for evaluating QiU2nd Approach Problem: it produces a very high number of entries on the nodes that

represent the QiU characteristics. And therefore, the definition of the probability tables is very laborious and

cumbersome. Solution: the introduction of synthetic nodes

3rd Approach

BNs for evaluating QiU3rd Approach A synthetic node among sub-characteristics of each

EQ characteristic and each QiU characteristic.

BNs for evaluating QiU3rd Approach Advantages: It reduces the number of entries in the probability tables. It avoids the undesirable influence of EQ sub-characteristics on the QiU characteristics when they do not have

a direct relationship

This network achieved a finer granularity while avoiding inconsistent relations Disadvantages: the concept of external quality characteristic is lost.

However, we could easily create four individual BNs, one for each QiU characteristic, and then combine them to form the complete Bayesian Network.

Each QiU characteristic can be studied independently

Contents

Introduction1

ISO/IEC 91262

Conclusions5

Conclusions We have proposed to change the focus of the Evaluation of

the Overall Quality of a Software Product Evaluation should be focused on the QiU – and then use a

backwards analysis for predicting the minimum acceptance levels for EQ (sub)characteristics that ensure the required level of QiU

We have shown how to build a BNs for conducting such analysis

Future work Empirically validate the proposal by:

exercising the BNs in several contexts of use. adapting the BNs to the specific peculiarities of each context checking that the BNs learn as they should for these contexts

Refine this approach by combining it with some Principal Component Analysis during the initial definition of the BN

Provide a useful input to the ISO Working Group defining the new SQUARE family of standards based on our researches

LOGO Evaluating Quality-in-Use Using Bayesian Networks M.A. Moraga 1, M.F. Bertoa 2, M.C. Morcillo...

Documents

Transcript of LOGO Evaluating Quality-in-Use Using Bayesian Networks M.A. Moraga 1, M.F. Bertoa 2, M.C. Morcillo...

Ing. Pablo Morcillo Valdivia · CARTA DEL JEFE INDIO SEATTLE, A FRANKLIN PIERCE, PRESIDENTE DE LOS ESTADOS UNIDOS DE AMÉRICA (1854) “El hombre no …

Allianz arena guillermo vallecillo

Llibres - COnnecting REpositoriesLlibres MARÍA DEL CARMEN HURTADO; MATILDE MORCILLO; MARÍA DOLORES GONZÁLEZ; AURORA GALÁN Y ÁNGEL ARJONA. Historia y vida de las mujeres en Albacete

Poster morcillo et al tuber borchii micorrhization depending on host tree and on stage of inoculation

Peter Vallecillo l Where is the American GI Forum l Voice of the Mainland l 7 24 12

Jose E. Rivera, Antonio Vallecillo Universidad de Málaga, Spain TOOLS Europe 2008, Zurich.

Biblioteca Virtual CINADE · Cubierta: Esther Morcillo Bernal. Imprime: T.G. ARTE, Juberías & cÍA., s.L. Rubén Dario, s/n. - Tif. y Fax: (958) 42 OO 40 18200-MARACENA (Granada)

Desconferencia #FactoriaQ: 10 claves para el emprendimiento digital, Francisco Morcillo

Artist Portfolio Gabriel Vallecillo

KM C654e-20190524141901...Maria Raquel Morcillo-Gallego Bobbie Massengale That is the same number of employees currently in our Chartwells food service program. How did the district

J.E. Rivera, D. Ruiz-González, F. López-Romero, J. Bautista, and A. Vallecillo MtATL 09 Nantes, July 09.

Families of Vallecillo, Nuevo Leon, Mexico Volume …Families of Vallecillo, Nuevo Leon, Mexico Volume Two Page 5 36 i Maria Francisca MARTINEZ, christened 14 Oct 1832 in Cerralvo,

ESCRITURA Y PUBLICACION DE ARTICULOS BIOMEDICOS TITULO, RESUMEN Y AUTORIA DR. NICOLAS SABILLON VALLECILLO ESPECIALISTA EN ANATOMIA PATOLOGICA EX DIRECTOR.

í (Guatemala) - iht.hn de Angeles Vallecillo Veracruz Villa de San Antonio ... Regiones Turísticas de Honduras ... Manufactura y venta de artesanias * Centro de Convenciones Playas

DISCUSSION PAPER...Climate Alliance: Dag Schulze, Miguel Morcillo, Carsten Kuhn deENet e.V./ IdE: Peter Moser, Beate Fischer, Lioba Kucharczak EKOenergy: Steven Vanholme European Renewable

The plasticizer benzyl butyl phthalate (BBP) alters the ... · Óscar Herrero⇑, Rosario Planelló, Gloria Morcillo Grupo de Biología y Toxicología Ambiental, Facultad de Ciencias,

Morcillo et alFig. 1. Relation between salinity and steel corrosion (Morcillo et al., 1999) The wind, which stirs up and transports particles of sea water, is the force responsible

MANUEL BENÍTEZ CARRASCO Y - Editorial ComaresEspecial dedicatoria para la niña-mujer —al decir de los versos del poeta— Maribel Morcillo Esteban. Desde el limbo de los dones

Official Website of the Professional Regulation …( Abarra, Romulo Morcillo - Bd. of Real Estate Salesperson Res. No. Page 3 Tagnawa, Jelic Bergonia ) RESOLVED FURTHER, that the validity

Using UML for Writing and Reasoning about ODP Policies Javier Herrador, Francisco Durán, Antonio Vallecillo Felipe García, Manuel Roldán Dept. Lenguajes.