Continuous Learning of the Structure of Bayesian Networks: A Mapping Study

Bayesian networks can be built based on knowledge, data, or both. Independent of the source of information used to build the model, inaccuracies might occur or the application domain might change. Therefore, there is a need to continuously improve the model during its usage. As new data are collected, algorithms to continuously incorporate the updated knowledge can play an essential role in this process. In regard to the continuous learning of the Bayesian network’s structure, the current solutions are based on its structural refinement or adaptation. Recent researchers aim to reduce complexity and memory usage, allowing to solve complex and large-scale practical problems. This study aims to identify and evaluate solutions for the continuous learning of the Bayesian network’s structures, as well as to outline related future research directions. Our attention remains on the structures because the accurate parameters are completely useless if the structure is not representative

Um processo baseado em redes bayesianas para avaliação da aplicação do scrum em projetos de software.

O aumento na utilização de métodos ágeis tem sido motivado pela necessidade de respostas rápidas a demandas de um mercado volátil na área de software. Em contraste com os tradicionais processos dirigidos a planos, métodos ágeis são focados nas pessoas, orientados à comunicação, flexíveis, rápidos, leves, responsivos e dirigidos à aprendizagem e melhoria contínua. Como consequência, fatores subjetivos tais como colaboração, comunicação e auto-organização são chaves para avaliar a maturidade do desenvolvimento de software ágil. O Scrum, focado no gerenciamento de projetos, é o método ágil mais popular. Ao ser adotado por uma equipe, a aplicação do Scrum deve ser melhorada continuamente sendo complementado com práticas e processos de desenvolvimento e gerenciamento ágeis. Apesar da Reunião de Retrospectiva, evento do Scrum, ser um período reservado ao final de cada sprint para a equipe refletir sobre a melhoria do método de desenvolvimento, não há procedimentos claros e específicos para a realização da mesma. Na literatura, há diversas propostas de soluções, embora nenhuma consolidada, para tal. Desta forma, o problema em questão é: como instrumentar o Scrum para auxiliar na melhoria contínua do método de desenvolvimento com foco na avaliação do processo de engenharia de requisitos, equipe de desenvolvimento e incrementos do produto? Nesta tese, propõe-se um processo sistemático baseado em redes bayesianas para auxiliar na avaliação da aplicação do Scrum em projetos de software, instrumentando o método para auxiliar na sua melhoria contínua com foco na avaliação do processo de engenharia de requisitos, equipe de desenvolvimento e incrementos do produto. A rede bayesiana foi construída por meio de um processo de Engenharia de Conhecimento de Redes Bayesianas. Uma base de dados, elicitada de dezoito projetos reais de uma empresa, foi coletada por meio de um questionário. Essa base de dados foi utilizada para avaliar a acurácia da predição da Rede Bayesiana. Como resultado, a previsão foi correta para quatorze projetos (acurácia de 78%). Dessa forma, conclui-se que o modelo é capaz de realizar previsões com acurácia satisfatória e, dessa forma, é útil para auxiliar nas tomadas de decisões de projetos Scrum.The use of Agile Software Development (ASD) is increasing to satisfy the need to respond to fast moving market demand and gain market share. In contrast with traditional plan-driven processes, ASD are people and communication-oriented, flexible, fast, lightweight, responsive, driven for learning and continuous improvement. As consequence, subjective factors such as collaboration, communication and self-management are key to evaluate the maturity of agile adoption. Scrum, which is focused on project management, is the most popular agile method. Whenever adopted, the usage of Scrum must be continuously improved by complementing it with development and management practices and processes. Even though the Retrospective Meeting, a Scrum event, is a period at the end of each sprint for the team to assess the development method, there are no clear and specific procedures to conduct it. In literature, there are several, but no consolidated, proposed solutions to assist on ASD adoption and assessment. Therefore, the research problem is: how to instrument Scrum to assist on the continuous improvement of the development method focusing on the requirements engineering process, development team and product increment? In this thesis, we propose a Bayesian networks-based process to assist on the assessment of Scrum-based projects, instrumenting the software development method to assist on its continuous improvement focusing on the requirements engineering process, development team and product increments. We have built the Bayesian network using a Knowledge Engineering Bayesian Network (KEBN) process that calculates the customer satisfaction given factors of the software development method. To evaluate its prediction accuracy, we have collected data from 18 industry projects from one organization through a questionnaire. As a result, the prediction was correct for fourteen projects (78% accuracy). Therefore, we conclude that the model is capable of accurately predicting the customer satisfaction and is useful to assist on decision-support on Scrum projects

Secure Cloud Storage with Client-Side Encryption Using a Trusted Execution Environment

With the evolution of computer systems, the amount of sensitive data to be stored as well as the number of threats on these data grow up, making the data confidentiality increasingly important to computer users. Currently, with devices always connected to the Internet, the use of cloud data storage services has become practical and common, allowing quick access to such data wherever the user is. Such practicality brings with it a concern, precisely the confidentiality of the data which is delivered to third parties for storage. In the home environment, disk encryption tools have gained special attention from users, being used on personal computers and also having native options in some smartphone operating systems. The present work uses the data sealing, feature provided by the Intel Software Guard Extensions (Intel SGX) technology, for file encryption. A virtual file system is created in which applications can store their data, keeping the security guarantees provided by the Intel SGX technology, before send the data to a storage provider. This way, even if the storage provider is compromised, the data are safe. To validate the proposal, the Cryptomator software, which is a free client-side encryption tool for cloud files, was integrated with an Intel SGX application (enclave) for data sealing. The results demonstrate that the solution is feasible, in terms of performance and security, and can be expanded and refined for practical use and integration with cloud synchronization services

Issues in the Probability Elicitation Process of Expert-Based Bayesian Networks

A major challenge in constructing a Bayesian network (BN) is defining the node probability tables (NPT), which can be learned from data or elicited from domain experts. In practice, it is common not to have enough data for learning, and elicitation from experts is the only option. However, the complexity of defining NPT grows exponentially, making their elicitation process costly and error-prone. In this research, we conducted an exploratory study through a literature review that identified the main issues related to the task of probability elicitation and solutions to construct large-scale NPT while reducing the exposure to these issues. In this chapter, we present in detail three semiautomatic methods that reduce the burden for experts. We discuss the benefits and drawbacks of these methods, and present directions on how to improve them

AVALIAÇÃO DE MODELOS DE PREDITIVOS DE REGRESSÃO PARA ESTIMAR ESFORÇO DE SOFTWARE

Effort estimation is a critical task in the software development life cycle. Inaccurate estimations might cause customer dissatisfaction and reduce product quality. In this paper, we evaluate the use of machine learning-based techniques to estimate effort for software tasks. We executed an empirical study based on the [Desharnais 1989] dataset and compared the predictions of three models: Linear Regression (LR), Support Vector Machine (SVM) and K-Nearest Neighbor (KNN) algorithms. The results of our study show that some software metrics are more important to estimate software effort than others. Also based on the quadratic error, which calculates how close the distance of a square regression line is to a set of points, we can successfully estimate 76% of the software effort for the dataset studied, where the predictive models created show only 3% difference between them.A estimativa de esforço é uma tarefa crítica no ciclo de vida de desenvolvimento de software. Estimativas imprecisas podem causar insatisfação do cliente e reduzir a qualidade do produto. Neste artigo, avaliamos o uso de técnicas baseadas em aprendizado de máquina para estimar o esforço para tarefas de software. Executamos um estudo empírico baseado no conjunto de dados [Desharnais 1989] e comparamos as previsões de três modelos: Regressão Linear (LR), Support Vector Machine (SVM) e K-Nearest Neighbor (KNN). Os resultados do nosso estudo mostram que algumas métricas de software são mais importantes para estimar o esforço de software do que outras. Também com base no erro quadrático, que calcula quão próxima a distância de uma linha de regressão quadrada é de um conjunto de pontos, podemos estimar com sucesso 76% do esforço de software para o conjunto de dados estudado, onde os modelos preditivos criados mostram apenas 3% diferença entre eles

A Bayesian network framework for project cost, benefit and risk analysis with an agricultural development case study

Successful implementation of major projects requires careful management of uncertainty and risk. Yet such uncertainty is rarely effectively calculated when analysing project costs and benefits. This paper presents a Bayesian Network (BN) modelling framework to calculate the costs, benefits, and return on investment of a project over a specified time period, allowing for changing circumstances and trade-offs. The framework uses hybrid and dynamic BNs containing both discrete and continuous variables over multiple time stages. The BN framework calculates costs and benefits based on multiple causal factors including the effects of individual risk factors, budget deficits, and time value discounting, taking account of the parameter uncertainty of all continuous variables. The framework can serve as the basis for various project management assessments and is illustrated using a case study of an agricultural development project