Adaptive Mean Value Function Based Quality Assessment of Software Reliable Growth Models

Software growth models aims for reliability of the application over a period of time. Assessment of such models is of great interest since many faults arises with the models during the operation over a span of time. In this paper a adaptive mean value function based testing and estimation of the parameters were discussed. The proposed approach is also compared against the conventional testing approaches and found that the proposed method able to detect the fault under different scenario and proves to give better performance under a constrained environment. Keywords: Software reliability, Growth models, testing analysis, Fault detection and correction

A Review of Software Reliability Testing Techniques

In the era of intelligent systems, the safety and reliability of software have received more attention. Software reliability testing is a significant method to ensure reliability, safety and quality of software. The intelligent software technology has not only offered new opportunities but also posed challenges to software reliability technology. The focus of this paper is to explore the software reliability testing technology under the impact of intelligent software technology. In this study, the basic theories of traditional software and intelligent software reliability testing were investigated via related previous works, and a general software reliability testing framework was established. Then, the technologies of software reliability testing were analyzed, including reliability modeling, test case generation, reliability evaluation, testing criteria and testing methods. Finally, the challenges and opportunities of software reliability testing technology were discussed at the end of this paper

Quantitative Analysis of Domain Testing Effectiveness.

The criticality of the applications modeled by the real-time software places stringent requirements on software quality before deploying into real use. Though automated test tools can be used to run a large number of tests efficiently, the functionality of any test tool is not complege without providing a means for analyzing the test results to determine potential problem sub-domains and sub-domains that need to be covered, and estimating the reliability of the modeled system. This thesis outlines a solution strategy and implementation of that strategy for deriving quantitative metrics from domain testing of real-time control software tested via simulation. The key portion of this thesis addresses the combinatorial problems involved with effective evaluation of test coverage and provides the developer with reliability metrics from testing of the software to gain confidence in the test phase of development. The two approaches for reliability analysis- time domain and input domain approaches are studied and a hybrid approach that combines the strengths of both these approaches is proposed. A Reliability analysis Test Tool (RATT) has been developed to implement the proposed strategies. The results show that the metrics are practically feasible to compute and can be applied to most real-time software

Analysis of costs and delivery intervals for multiple-release software

Project managers of large software projects, and particularly those associated with Internet Business-to-Business (B2B) or Business-to-Customer (B2C) applications, are under pressure to capture market share by delivering reliable software with cost and timing constraints. An earlier delivery time may help the E-commerce software capture a larger market share. However, early delivery sometimes means lower quality. In addition, most of the time the scale of the software is so large that incremental multiple releases are warranted. A Multiple-Release methodology has been developed to optimize the most efficient and effective delivery intervals of the various releases of software products, taking into consideration software costs and reliability. The Multiple-Release methodology extends existing software cost and reliability models, meets the needs of large software development firms, and gives a navigation guide to software industrial managers. The main decision factors for the multiple releases include the delivery interval of each release, the market value of the features in the release, and the software costs associated with testing and error penalties. The input of these factors was assessing using Design of Experiments (DOE). The costs included in the research are based on a salary survey of software staff at companies in the New Jersey area and on budgets of software development teams. The Activity Based Cost (ABC) method was used to determine costs on the basis of job functions associated with the development of the software. It is assumed that the error data behavior follows the Non-Homogeneous Poisson Processes (NHPP)

APPLICATION AND REFINEMENTS OF THE REPS THEORY FOR SAFETY CRITICAL SOFTWARE

With the replacement of old analog control systems with software-based digital control systems, there is an urgent need for developing a method to quantitatively and accurately assess the reliability of safety critical software systems. This research focuses on proposing a systematic software metric-based reliability prediction method. The method starts with the measurement of a metric. Measurement results are then either directly linked to software defects through inspections and peer reviews or indirectly linked to software defects through empirical software engineering models. Three types of defect characteristics can be obtained, namely, 1) the number of defects remaining, 2) the number and the exact location of the defects found, and 3) the number and the exact location of defects found in an earlier version. Three models, Musa's exponential model, the PIE model and a mixed Musa-PIE model, are then used to link each of the three categories of defect characteristics with reliability respectively. In addition, the use of the PIE model requires mapping defects identified to an Extended Finite State Machine (EFSM) model. A procedure that can assist in the construction of the EFSM model and increase its repeatability is also provided. This metric-based software reliability prediction method is then applied to a safety-critical software used in the nuclear industry using eleven software metrics. Reliability prediction results are compared with the real reliability assessed by using operational failure data. Experiences and lessons learned from the application are discussed. Based on the results and findings, four software metrics are recommended. This dissertation then focuses on one of the four recommended metrics, Test Coverage. A reliability prediction model based on Test Coverage is discussed in detail and this model is further refined to be able to take into consideration more realistic conditions, such as imperfect debugging and the use of multiple testing phases

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

Software Engineering Laboratory Series: Proceedings of the Twenty-Second Annual Software Engineering Workshop

The Software Engineering Laboratory (SEL) is an organization sponsored by NASA/GSFC and created to investigate the effectiveness of software engineering technologies when applied to the development of application software. The activities, findings, and recommendations of the SEL are recorded in the Software Engineering Laboratory Series, a continuing series of reports that includes this document