A Feature Ranking Algorithm in Pragmatic Quality Factor Model for Software Quality Assessment

Software quality is an important research area and has gain considerable attention from software engineering community in identification of priority quality attributes in software development process. This thesis describes original research in the field of software quality model by presenting a Feature Ranking Algorithm (FRA) for Pragmatic Quality Factor (PQF) model. The proposed algorithm is able to improve the weaknesses in PQF model in updating and learning the important attributes for software quality assessment. The existing assessment techniques lack of the capability to rank the quality attributes and data learning which can enhance the quality assessment process. The aim of the study is to identify and propose the application of Artificial Intelligence (AI) technique for improving quality assessment technique in PQF model. Therefore, FRA using FRT was constructed and the performance of the FRA was evaluated. The methodology used consists of theoretical study, design of formal framework on intelligent software quality, identification of Feature Ranking Technique (FRT), construction and evaluation of FRA algorithm. The assessment of quality attributes has been improved using FRA algorithm enriched with a formula to calculate the priority of attributes and followed by learning adaptation through Java Library for Multi Label Learning (MULAN) application. The result shows that the performance of FRA correlates strongly to PQF model with 98% correlation compared to the Kolmogorov-Smirnov Correlation Based Filter (KSCBF) algorithm with 83% correlation. Statistical significance test was also performed with score of 0.052 compared to the KSCBF algorithm with score of 0.048. The result shows that the FRA was more significant than KSCBF algorithm. The main contribution of this research is on the implementation of FRT with proposed Most Priority of Features (MPF) calculation in FRA for attributes assessment. Overall, the findings and contributions can be regarded as a novel effort in software quality for attributes selection

Connection between version control operations and quality change of the source code

Software erosion is a well-known phenomena, meaning that software quality is continuously decreasing due to the ever-ongoing modifications in the source code. In this research work we investigated this phenomena by studying the impact of version control commit operations (add, update, delete) on the quality of the code. We calculated the ISO/IEC 9126 quality attributes for thousands of revisions of an industrial and three open-source software systems with the help of the Columbus Quality Model. We also collected the cardinality of each version control operation type for every investigated revision. We performed Chisquared tests on contingency tables with rows of quality change and columns of version control operation commit types. We compared the results with random data as well. We identified that the relationship between the version control operations and quality change is quite strong. Great maintainability improvements are mostly caused by commits containing Add operation. Commits containing file updates only tend to have a negative impact on the quality. Deletions have a weak connection with quality, and we could not formulate a general statement

Evidentiary treatment of computer-produced material : a reliability based evaluation

Tese de doutoramento em Engenharia Mecânica (Pré-Bolonha), Especialidade de Tecnologia da Produção, apresentada à Faculdade de Ciências e Tecnologia da Universidade de CoimbraCoatings are frequently applied on molds and accessories for the glass industry in order to restrict surface degradation such as oxidation, corrosion, abrasion and wear of the structural material, thereby decreasing the maintenance costs and increasing the lifetime and performance of components. However, in order to obtain accurate lifetime expectancies and performance of the coatings it is necessary to have a complete reliable understanding of their properties. This thesis is on the improvement of the surface properties and integrity of molds, in order to increase their durability, through the application of different types of coatings. Two methodologies were followed to reach such demands: 1 - synthesis, optimization and characterization of coatings currently used in molds surface protection (Ni-based alloys deposited by Plasma Transferred Arc); 2 - synthesis and characterization of new coatings with improved functionalities, deposited by emergent deposition processes such as Atmospheric Plasma Spraying and DC Reactive Magnetron Sputtering. In a first step it was intended to optimize Ni-based coatings deposited by PTA process, studying the effect of substrate dilution on the properties of coatings. In the second part, two different coating systems were evaluated. The first topic investigated the effect of ZrO2 additions on the microstructure, mechanical properties and tribological behavior to Ni-based alloy coatings deposited by APS process, whilst, in the second the influence of V additions on the properties of TiSi(V)N thin films, containing different Si and V contents, deposited by DC reactive magnetron sputtering, was evaluated. The main results to be enhanced are described below for each coating system investigated. The dilution of the substrate showed strongly influence the structure and consequently the hardness, oxidation resistance and tribological behavior of coatings. It was observed that increasing dilution had a detrimental effect on the hardness, oxidation resistance and tribological behavior of coatings at room temperature due to base material incorporation. However, in the latter it demonstrated to have a beneficial effect at high temperature due to the fast formation of oxide layers which protect the coating surface against wear. The post-weld heat treatment performed at coatings reduced the hardness of the partially melted and heat affected zones without affecting the coatings hardness. Furthermore, coatings hardness and wear resistance was increased with annealing treatment. Thus, the best performing coating could only be achieved by, selecting the proper deposition conditions that give the best correlation among mechanical properties, level of oxidation and wear resistance of coatings. ZrO2 additions promoted different impact on the microstructure of a Ni-based alloy, when coatings were deposited using powders mixed by mechanical alloying or using separated powders. A homogeneous and compact microstructure with small zirconia particles evenly distributed in the matrix was obtained in the first case, while a porous microstructure, full of semi-melted Ni powders with large particles of ZrO2 entrapped in their boundaries suggesting a brittle behavior was obtained in the second. In both cases the hardness and wear behavior of ZrO2 rich coatings in relation to the Ni-based one, was improved. However, coatings deposited by powders prepared my mechanical alloying revealed to be much more performing due to their compact structure and even distribution of zirconia. All the APS coatings showed higher hardness values than the Ni-based coatings deposited by PTA, however, their micro-abrasion resistance revealed to be worst, due to the lack of cohesion between powders. The structure of V rich coatings analysed by XRD revealed that V incorporations to the TiSiN system shift the peaks to higher angles, indicating a substitutional solid solution due to the substitution of Ti by smaller V atoms. On the other hand, X-ray diffraction analyses performed at the TiSiN films revealed that the stoichiometric nanocomposite structure for the control of vanadium diffusion was not formed. In fact Si incorporation at the TiN system revealed to shift the diffraction peaks to higher angles, which in combination to the same level of compressive residual stresses measured for all the Si rich films, indicted substitutional solid solution formation. V additions showed successfully increase the hardness and tribological behavior of TiSiVN films. The hardness improvement with V incorporations has shown to be a result of the substitutional solid solution formation, whilst, the improvement of the tribological properties is related to the V2O5 phase formation on the sliding contact that acts as a lubricious tribo-film, which protects the coating from wear. The oxidation resistance of Si and V rich coatings showed to be strongly influenced by their structure. Si and V incorporations at the TiN and TiSiN systems, showed improve and abruptly decrease the oxidation resistance of films, respectively. The oxidation resistance decrease of V rich coatings was attributed to the rapid V ions diffusion throughout the oxide scale, which inhibited the formation of a continuous protective silicon oxide layer, as opposed to TiSiN films case, where a continuous and protective SiO2 layer was built leading to a much lower oxidation weight gain over time. V rich coatings showed lower oxidation resistance than Ni-based coatings PTA, but superior hardness values (some orders of magnitude higher) and greater tribological behavior than PTA and APS deposited coatings.Diferentes tipos de revestimentos são frequentemente aplicados em moldes e acessórios para a indústria do vidro, de forma a atenuar a degradação das suas superfícies, devida às extremas condições de oxidação, corrosão, abrasão e desgaste de uso a que estão sujeitos, diminuindo desta forma os custos de manutenção e aumentando o tempo de vida e o desempenho destes componentes. No entanto, de forma a maximizar o desempenho dos revestimentos, é necessário ter uma completa e fiável compreensão das suas propriedades. Esta tese é totalmente dedicada à melhoria das propriedades da superfície dos moldes, de forma a aumentar a sua durabilidade e performance, através da aplicação de diferentes tipos de revestimentos. No sentido de dar cumprimento a este desafio, duas metodologias foram seguidas: 1 - síntese, optimização e caracterização de revestimentos actualmente usados na protecção da superfície dos moldes (ligas à base de Ni depositadas por PTA (plasma transferred arc)); 2 - síntese e caracterização de novos revestimentos mais resistente e com melhores propriedades, depositados por processos de deposição emergentes no mercado, tal como são os casos do APS (atmospheric plasma spraying) e do PVD (physical vapor deposition). Primeiramente estudou-se o efeito da diluição do material base nas propriedades de uma liga de níquel depositada por PTA usada actualmente na protecção da superfície dos moldes. Na segunda parte diferentes sistemas de revestimento foram avaliados. O primeiro estudo incidiu sobre o efeito da adição de ZrO2 nas propriedades mecânicas, microestrutura e comportamento tribológico de uma liga de Ni depositada por APS, enquanto que o segundo estudo recaiu na análise da influência da adição de V nas propriedades de revestimentos cerâmicos de TiSiN, contendo diferentes teores de Si e V, depositados por PVD. Os principais resultados alcançados durante este trabalho são resumidos seguidamente, para cada um dos sistemas de revestimentos analisados. A diluição do substrato mostrou influenciar a estrutura e consequentemente diminuir a dureza, resistência à oxidação e resistência ao desgaste à temperatura ambiente dos revestimentos. No entanto, teve um efeito benéfico no comportamento tribológico a temperaturas elevadas, devido à rápida formação de uma camada de óxido, que mostrou proteger a superfície contra o desgaste. O tratamento térmico efectuado aos revestimentos após deposição reduziu com sucesso a dureza das zonas termicamente afectada pelo calor e parcialmente fundida, sem alterar a dureza da zona fundida. Além disso, o tratamento de envelhecimento realizado aos revestimentos mostrou aumentar a sua dureza e a sua resistência ao desgaste com a exposição à temperatura. Assim, o revestimento com melhor desempenho só pode ser obtido seleccionando as condições de deposição que originem o melhor compromisso entre propriedades mecânicas, nível de oxidação e de resistência ao desgaste. A adição de zircónia à liga de níquel depositada por APS, usando pós de Ni e ZrO2 misturados por síntese mecânica e pós separados promoveu diferente impacto na microestrutura dos revestimentos. Quando depositados com pós preparados por síntese mecânica, os revestimentos exibiram uma estrutura homogénea e compacta com pequenas partículas de zircónica uniformemente distribuídas al longo da matriz de Ni. Por outro lado, quando depositados separadamente obteve-se uma estrutura extremamente porosa com pós de Ni semi-fundidos e com partículas de ZrO2 aprisionadas na sua interface, sugerindo um comportamento frágil. Independente do procedimento de deposição usado, em ambos os casos a dureza e a resistência ao desgaste dos revestimentos foi melhorada com a adição de ZrO2. Contudo, os revestimentos depositados usando pós produzidos por síntese mecânica revelaram possuir uma maior performance, devido à sua estrutura compacta e distribuição uniforme de ZrO2. Todos os revestimentos depositados por APS revelaram possuir valores de dureza superiores aos revestimentos depositados por PTA, no entanto, a sua resistência à abrasão mostrou ser bastante inferior devido à falta de coesão entre pós. As análises de difracção de raio-X realizadas aos filmes ricos em V revelaram que os picos de difracção se deslocam para ângulos superiores com o aumento do teor em V, indicando a formação de uma solução sólida substitucional. Por outro lado, a análise realizada aos revestimentos de TiSIN revelou que a estrutura estequiométrica nanocompósita, requerida para o controlo da difusão de vanádio não foi formada. De facto, a adição de Si ao sistema TiN revelou também deslocar os picos de difracção para ângulos superiores, o que em combinação com o mesmo nível de tensões residuais medido nos diferentes revestimentos, indica a formação de uma solução sólida substitucional. A Adição de V ao sistema TiSiN mostrou aumentar com sucesso as suas propriedades mecânicas e tribológicas. O aumento da dureza com a adição de vanádio foi atribuído à formação da solução sólida substitucional, enquanto, a melhoria das propriedades tribológicas está relacionada com a formação da fase V2O5, no topo da superfície do filme, a qual age como lubrificante sólido, e portanto protege o revestimento de desgaste. A resistência à oxidação de revestimentos ricos em Si e V mostrou ser fortemente influenciada pela sua estrutura. A adição de Si e V aos sistemas TiN e TiSiN, respectivamente, mostrou aumentar e abruptamente reduzir a resistência à oxidação dos filmes. A diminuição da resistência a oxidação dos revestimentos ricos em V foi atribuída à rápida difusão dos iões de V através da camada de óxido, o que inibiu a formação de uma camada contínua e protectora de óxido de silício, contrariamente ao que acontece nos revestimentos TiSiN, onde uma camada contínua e protectora de Si-O foi formada, levando a menores taxas de ganho de massa devido à oxidação com o tempo. Os filmes ricos em V apresentaram menor resistência à oxidação do que os revestimentos espessos depositados por PTA, no entanto, a sua dureza e resistência ao desgaste mostrou ser bastante superior aos dos revestimentos depositados por PTA e APS

Justified test foci definition an empirical approach

Since complete testing is not possible, testers have to focus their effort on those parts of the software which they expect to have defects, the test foci. Despite the crucial importance of a systematic and justified definition of the test foci, this task is not well established in practice. Usually, testing resources are uniformly distributed among all parts of the software. A risk of this approach is that parts which contain defects are not sufficiently tested, whereas areas that do not contain defects attain too much consideration. In this thesis, a systematic approach is introduced that allows testers to make justified decisions on the test foci. For this purpose, structural as well as historical characteristics of the software’s past releases are analysed visually and statistically in order to find indicators for the software’s defects. Structural characteristics refer to the internal structure of the software. This thesis concentrates on the analysis of bad software characteristics, also known as “bad smells”. Historical characteristics considered in this thesis are the software’s change history and the software’s age. Simple and combined analyses of defect variance are introduced in order to determine indicators for defects in software. For this purpose, the defect variance analysis diagram is used to explore the relationship between the software’s characteristics and its faultiness visually. Then, statistical procedures are applied in order to determine whether the results obtained visually are statistically significant. The approach is validated in the context of open source development as well as in an industrial setting. For this purpose, seven open source programs as well as several releases of a commercial program are analysed. Thus, the thesis increases the empirical body of knowledge concerning the empirical validation of indicators for defects in software. The results show that there is a subset of bad smells that are well suited as indicators for defects in software. A good indicator in most of all analysed programs is the “God Class” bad smell. Among the historical characteristics analysed in the industrial context, the number of distinct authors as well as the number of changes performed to a file proved to be useful indicators for defects in software

Measuring, monitoring, and assessing software process using PAMPA 2.0 knowledge-based system

My research is about monitoring the software development process to assess Capability maturity level. Capability Maturity Model (CMM) was developed to improve the software process based on subjective assessment by teams of experts. We propose an objective CMM assessment, which replaces expensive and time-consuming human effort by a knowledge-based system. Compared to Subjective CMM assessment, Objective CMM assessment can be less expensive, takes less time, and is easy to estimate the software development environment maturity. The accuracy of Objective CMM assessment can be the same as Subjective CMM assessment if enough activities are represented as objective activities. For example, if subjective activities total 80 % and objective activities total 20 %, then the accuracy of Objective CMM assessment is not reliable. It would be reliable if the objective activity is increased up to 80% from 20%. This dissertation presents how to change from Subjective CMM assessment to Objective CMM assessment, and we will prove that Objective CMM Assessment is effective

An Empirical Study of Process Discipline and Software Quality

There is a widespread, but not universal, belief in the software community that software organizations and projects can systematically improve their ability to meet commitments and build high-quality products using principles of software quality management. Quality affects cost and schedule, therefore the engineering practices that affect quality are also a management concern. Understanding the factors that influence software quality is crucial to the continuing maturation of the software industry; an improved understanding of software quality drivers will help software engineers and managers make more informed decisions in controlling and improving the software process.My research is motivated by a desire to understand the effect of disciplined processes and effective teams on improving performance and lessening variability with respect to software quality. Classroom data provides insight into interpersonal differences between competent professionals as increasingly disciplined processes are adopted. Project data using similar processes enables an exploration of the impact of effective teams on software quality.My results show that:* Program size, programmer ability, and disciplined processes significantly affect software quality.* Factors frequently used as surrogates for programmer ability, e.g., years of experience, and technology, e.g., programming language, do not significantly impact software quality.* Recommended practices are not necessarily followed even when processes are consistently performed, e.g., peer reviews may be consistently performed, but the review rates may exceed recommended practice for effective reviews.* When moving from ad hoc processes to disciplined processes, top-quartile performers improve more than 2X; bottom-quartile performers improve more than 4X. * Rigorous statistical techniques that allow for individual differences confirm the importance of process discipline and following recommended practice for improving software quality