Test generation for high coverage with abstraction refinement and coarsening (ARC)

Testing is the main approach used in the software industry to expose failures. Producing thorough test suites is an expensive and error prone task that can greatly benefit from automation. Two challenging problems in test automation are generating test input and evaluating the adequacy of test suites: the first amounts to producing a set of test cases that accurately represent the software behavior, the second requires defining appropriate metrics to evaluate the thoroughness of the testing activities. Structural testing addresses these problems by measuring the amount of code elements that are executed by a test suite. The code elements that are not covered by any execution are natural candidates for generating further test cases, and the measured coverage rate can be used to estimate the thoroughness of the test suite. Several empirical studies show that test suites achieving high coverage rates exhibit a high failure detection ability. However, producing highly covering test suites automatically is hard as certain code elements are executed only under complex conditions while other might be not reachable at all. In this thesis we propose Abstraction Refinement and Coarsening (ARC), a goal oriented technique that combines static and dynamic software analysis to automatically generate test suites with high code coverage. At the core of our approach there is an abstract program model that enables the synergistic application of the different analysis components. In ARC we integrate Dynamic Symbolic Execution (DSE) and abstraction refinement to precisely direct test generation towards the coverage goals and detect infeasible elements. ARC includes a novel coarsening algorithm for improved scalability. We implemented ARC-B, a prototype tool that analyses C programs and produces test suites that achieve high branch coverage. Our experiments show that the approach effectively exploits the synergy between symbolic testing and reachability analysis outperforming state of the art test generation approaches. We evaluated ARC-B on industry relevant software, and exposed previously unknown failures in a safety-critical software component

Developing a distributed electronic health-record store for India

The DIGHT project is addressing the problem of building a scalable and highly available information store for the Electronic Health Records (EHRs) of the over one billion citizens of India

Joint University Program for Air Transportation Research, 1990-1991

The goals of this program are consistent with the interests of both NASA and the FAA in furthering the safety and efficiency of the National Airspace System. Research carried out at the Massachusetts Institute of Technology (MIT), Ohio University, and Princeton University are covered. Topics studied include passive infrared ice detection for helicopters, the cockpit display of hazardous windshear information, fault detection and isolation for multisensor navigation systems, neural networks for aircraft system identification, and intelligent failure tolerant control

Robust constraint satisfaction: invariant sets and predictive control

Set invariance plays a fundamental role in the design of control systems for constrained systems sincethe constraints can be satisfied for all time if and only if the initial state is contained inside an invariantset. This thesis is concerned with robust set invariance theory and its application to guaranteeingfeasibility in model predictive control.In the first part of this thesis, some of the main ideas in set invariance theory are brought togetherand placed in a general, nonlinear setting. The key ingredients in computing robust controllable andinvariant sets are identified and discussed. Following this, linear systems with parametric uncertaintyand state disturbances are considered and algorithms for computing the respective robust controllableand invariant sets are described. In addition to discussing linear systems, an algorithm for computingthe robust controllable sets for piecewise affine systems with state disturbances is described.In the second part, the ideas from set invariance are applied to the problem of guaranteeing feasibilityand robust constraint satisfaction in Model Predictive Control (MPC). A new sufficient condition isderived for guaranteeing feasibility of a given MPC scheme. The effect of the choice of horizons andconstraints on the feasible set of the MPC controller is also investigated. Following this, a necessaryand sufficient condition is derived for determining whether a given MPC controller is robustly feasible.The use of a robustness constraint for designing robust MPC controllers is discussed and it is shownhow this proposed scheme can be used to guarantee robust constraint satisfaction for linear systemswith parametric uncertainty and state disturbances. A new necessary and sufficient condition as wellas some new sufficient conditions are derived for guaranteeing that the proposed MPC scheme isrobustly feasible.The third part of this thesis is concerned with recovering from constraint violations. An algorithm ispresented for designing soft-constrained MPC controllers which guarantee constraint satisfaction, ifpossible. Finally, a mixed-integer programming approach is described for finding a solution whichminimises the number of violations in a set of prioritised constraints

Review on Control of DC Microgrids and Multiple Microgrid Clusters

This paper performs an extensive review on control schemes and architectures applied to dc microgrids (MGs). It covers multilayer hierarchical control schemes, coordinated control strategies, plug-and-play operations, stability and active damping aspects, as well as nonlinear control algorithms. Islanding detection, protection, and MG clusters control are also briefly summarized. All the mentioned issues are discussed with the goal of providing control design guidelines for dc MGs. The future research challenges, from the authors' point of view, are also provided in the final concluding part

Improving the process of analysis and comparison of results in dependability benchmarks for computer systems

Tesis por compendioLos dependability benchmarks (o benchmarks de confiabilidad en español), están diseñados para evaluar, mediante la categorización cuantitativa de atributos de confiabilidad y prestaciones, el comportamiento de sistemas en presencia de fallos. En este tipo de benchmarks, donde los sistemas se evalúan en presencia de perturbaciones, no ser capaces de elegir el sistema que mejor se adapta a nuestras necesidades puede, en ocasiones, conllevar graves consecuencias (económicas, de reputación, o incluso de pérdida de vidas). Por esa razón, estos benchmarks deben cumplir ciertas propiedades, como son la no-intrusión, la representatividad, la repetibilidad o la reproducibilidad, que garantizan la robustez y precisión de sus procesos. Sin embargo, a pesar de la importancia que tiene la comparación de sistemas o componentes, existe un problema en el ámbito del dependability benchmarking relacionado con el análisis y la comparación de resultados. Mientras que el principal foco de investigación se ha centrado en el desarrollo y la mejora de procesos para obtener medidas en presencia de fallos, los aspectos relacionados con el análisis y la comparación de resultados quedaron mayormente desatendidos. Esto ha dado lugar a diversos trabajos en este ámbito donde el proceso de análisis y la comparación de resultados entre sistemas se realiza de forma ambigua, mediante argumentación, o ni siquiera queda reflejado. Bajo estas circunstancias, a los usuarios de los benchmarks se les presenta una dificultad a la hora de utilizar estos benchmarks y comparar sus resultados con los obtenidos por otros usuarios. Por tanto, extender la aplicación de los benchmarks de confiabilidad y realizar la explotación cruzada de resultados es una tarea actualmente poco viable. Esta tesis se ha centrado en el desarrollo de una metodología para dar soporte a los desarrolladores y usuarios de benchmarks de confiabilidad a la hora de afrontar los problemas existentes en el análisis y comparación de resultados. Diseñada para asegurar el cumplimiento de las propiedades de estos benchmarks, la metodología integra el proceso de análisis de resultados en el flujo procedimental de los benchmarks de confiabilidad. Inspirada en procedimientos propios del ámbito de la investigación operativa, esta metodología proporciona a los evaluadores los medios necesarios para hacer su proceso de análisis explícito, y más representativo para el contexto dado. Los resultados obtenidos de aplicar esta metodología en varios casos de estudio de distintos dominios de aplicación, mostrará las contribuciones de este trabajo a mejorar el proceso de análisis y comparación de resultados en procesos de evaluación de la confiabilidad para sistemas basados en computador.Dependability benchmarks are designed to assess, by quantifying through quantitative performance and dependability attributes, the behavior of systems in presence of faults. In this type of benchmarks, where systems are assessed in presence of perturbations, not being able to select the most suitable system may have serious implications (economical, reputation or even lost of lives). For that reason, dependability benchmarks are expected to meet certain properties, such as non-intrusiveness, representativeness, repeatability or reproducibility, that guarantee the robustness and accuracy of their process. However, despite the importance that comparing systems or components has, there is a problem present in the field of dependability benchmarking regarding the analysis and comparison of results. While the main focus in this field of research has been on developing and improving experimental procedures to obtain the required measures in presence of faults, the processes involving the analysis and comparison of results were mostly unattended. This has caused many works in this field to analyze and compare results of different systems in an ambiguous way, as the process followed in the analysis is based on argumentation, or not even present. Hence, under these circumstances, benchmark users will have it difficult to use these benchmarks and compare their results with those from others. Therefore extending the application of these dependability benchmarks and perform cross-exploitation of results among works is not likely to happen. This thesis has focused on developing a methodology to assist dependability benchmark performers to tackle the problems present in the analysis and comparison of results of dependability benchmarks. Designed to guarantee the fulfillment of dependability benchmark's properties, this methodology seamlessly integrates the process of analysis of results within the procedural flow of a dependability benchmark. Inspired on procedures taken from the field of operational research, this methodology provides evaluators with the means not only to make their process of analysis explicit to anyone, but also more representative for the context being. The results obtained from the application of this methodology to several case studies in different domains, will show the actual contributions of this work to improving the process of analysis and comparison of results in dependability benchmarking for computer systems.Els dependability benchmarks (o benchmarks de confiabilitat, en valencià), són dissenyats per avaluar, mitjançant la categorització quantitativa d'atributs de confiabilitat i prestacions, el comportament de sistemes en presència de fallades. En aquest tipus de benchmarks, on els sistemes són avaluats en presència de pertorbacions, el no ser capaços de triar el sistema que millor s'adapta a les nostres necessitats pot tenir, de vegades, greus conseqüències (econòmiques, de reputació, o fins i tot pèrdua de vides). Per aquesta raó, aquests benchmarks han de complir certes propietats, com són la no-intrusió, la representativitat, la repetibilitat o la reproductibilitat, que garanteixen la robustesa i precisió dels seus processos. Així i tot, malgrat la importància que té la comparació de sistemes o components, existeix un problema a l'àmbit del dependability benchmarking relacionat amb l'anàlisi i la comparació de resultats. Mentre que el principal focus d'investigació s'ha centrat en el desenvolupament i la millora de processos per a obtenir mesures en presència de fallades, aquells aspectes relacionats amb l'anàlisi i la comparació de resultats es van desatendre majoritàriament. Açò ha donat lloc a diversos treballs en aquest àmbit on els processos d'anàlisi i comparació es realitzen de forma ambigua, mitjançant argumentació, o ni tan sols queden reflectits. Sota aquestes circumstàncies, als usuaris dels benchmarks se'ls presenta una dificultat a l'hora d'utilitzar aquests benchmarks i comparar els seus resultats amb els obtinguts per altres usuaris. Per tant, estendre l'aplicació dels benchmarks de confiabilitat i realitzar l'explotació creuada de resultats és una tasca actualment poc viable. Aquesta tesi s'ha centrat en el desenvolupament d'una metodologia per a donar suport als desenvolupadors i usuaris de benchmarks de confiabilitat a l'hora d'afrontar els problemes existents a l'anàlisi i comparació de resultats. Dissenyada per a assegurar el compliment de les propietats d'aquests benchmarks, la metodologia integra el procés d'anàlisi de resultats en el flux procedimental dels benchmarks de confiabilitat. Inspirada en procediments propis de l'àmbit de la investigació operativa, aquesta metodologia proporciona als avaluadors els mitjans necessaris per a fer el seu procés d'anàlisi explícit, i més representatiu per al context donat. Els resultats obtinguts d'aplicar aquesta metodologia en diversos casos d'estudi de distints dominis d'aplicació, mostrarà les contribucions d'aquest treball a millorar el procés d'anàlisi i comparació de resultats en processos d'avaluació de la confiabilitat per a sistemes basats en computador.Martínez Raga, M. (2018). Improving the process of analysis and comparison of results in dependability benchmarks for computer systems [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/111945TESISCompendi

Complex Event Processing as a Service in Multi-Cloud Environments

The rise of mobile technologies and the Internet of Things, combined with advances in Web technologies, have created a new Big Data world in which the volume and velocity of data generation have achieved an unprecedented scale. As a technology created to process continuous streams of data, Complex Event Processing (CEP) has been often related to Big Data and used as a tool to obtain real-time insights. However, despite this recent surge of interest, the CEP market is still dominated by solutions that are costly and inflexible or too low-level and hard to operate. To address these problems, this research proposes the creation of a CEP system that can be offered as a service and used over the Internet. Such a CEP as a Service (CEPaaS) system would give its users CEP functionalities associated with the advantages of the services model, such as no up-front investment and low maintenance cost. Nevertheless, creating such a service involves challenges that are not addressed by current CEP systems. This research proposes solutions for three open problems that exist in this context. First, to address the problem of understanding and reusing existing CEP management procedures, this research introduces the Attributed Graph Rewriting for Complex Event Processing Management (AGeCEP) formalism as a technology- and language-agnostic representation of queries and their reconfigurations. Second, to address the problem of evaluating CEP query management and processing strategies, this research introduces CEPSim, a simulator of cloud-based CEP systems. Finally, this research also introduces a CEPaaS system based on a multi-cloud architecture, container management systems, and an AGeCEP-based multi-tenant design. To demonstrate its feasibility, AGeCEP was used to design an autonomic manager and a selected set of self-management policies. Moreover, CEPSim was thoroughly evaluated by experiments that showed it can simulate existing systems with accuracy and low execution overhead. Finally, additional experiments validated the CEPaaS system and demonstrated it achieves the goal of offering CEP functionalities as a scalable and fault-tolerant service. In tandem, these results confirm this research significantly advances the CEP state of the art and provides novel tools and methodologies that can be applied to CEP research

Processamento de eventos complexos como serviço em ambientes multi-nuvem

Orientadores: Luiz Fernando Bittencourt, Miriam Akemi Manabe CapretzTese (doutorado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: O surgimento das tecnologias de dispositivos móveis e da Internet das Coisas, combinada com avanços das tecnologias Web, criou um novo mundo de Big Data em que o volume e a velocidade da geração de dados atingiu uma escala sem precedentes. Por ser uma tecnologia criada para processar fluxos contínuos de dados, o Processamento de Eventos Complexos (CEP, do inglês Complex Event Processing) tem sido frequentemente associado a Big Data e aplicado como uma ferramenta para obter informações em tempo real. Todavia, apesar desta onda de interesse, o mercado de CEP ainda é dominado por soluções proprietárias que requerem grandes investimentos para sua aquisição e não proveem a flexibilidade que os usuários necessitam. Como alternativa, algumas empresas adotam soluções de baixo nível que demandam intenso treinamento técnico e possuem alto custo operacional. A fim de solucionar esses problemas, esta pesquisa propõe a criação de um sistema de CEP que pode ser oferecido como serviço e usado através da Internet. Um sistema de CEP como Serviço (CEPaaS, do inglês CEP as a Service) oferece aos usuários as funcionalidades de CEP aliadas às vantagens do modelo de serviços, tais como redução do investimento inicial e baixo custo de manutenção. No entanto, a criação de tal serviço envolve inúmeros desafios que não são abordados no atual estado da arte de CEP. Em especial, esta pesquisa propõe soluções para três problemas em aberto que existem neste contexto. Em primeiro lugar, para o problema de entender e reusar a enorme variedade de procedimentos para gerência de sistemas CEP, esta pesquisa propõe o formalismo Reescrita de Grafos com Atributos para Gerência de Processamento de Eventos Complexos (AGeCEP, do inglês Attributed Graph Rewriting for Complex Event Processing Management). Este formalismo inclui modelos para consultas CEP e transformações de consultas que são independentes de tecnologia e linguagem. Em segundo lugar, para o problema de avaliar estratégias de gerência e processamento de consultas CEP, esta pesquisa apresenta CEPSim, um simulador de sistemas CEP baseado em nuvem. Por fim, esta pesquisa também descreve um sistema CEPaaS fundamentado em ambientes multi-nuvem, sistemas de gerência de contêineres e um design multiusuário baseado em AGeCEP. Para demonstrar sua viabilidade, o formalismo AGeCEP foi usado para projetar um gerente autônomo e um conjunto de políticas de auto-gerenciamento para sistemas CEP. Além disso, o simulador CEPSim foi minuciosamente avaliado através de experimentos que demonstram sua capacidade de simular sistemas CEP com acurácia e baixo custo adicional de processamento. Por fim, experimentos adicionais validaram o sistema CEPaaS e demonstraram que o objetivo de oferecer funcionalidades CEP como um serviço escalável e tolerante a falhas foi atingido. Em conjunto, esses resultados confirmam que esta pesquisa avança significantemente o estado da arte e também oferece novas ferramentas e metodologias que podem ser aplicadas à pesquisa em CEPAbstract: The rise of mobile technologies and the Internet of Things, combined with advances in Web technologies, have created a new Big Data world in which the volume and velocity of data generation have achieved an unprecedented scale. As a technology created to process continuous streams of data, Complex Event Processing (CEP) has been often related to Big Data and used as a tool to obtain real-time insights. However, despite this recent surge of interest, the CEP market is still dominated by solutions that are costly and inflexible or too low-level and hard to operate. To address these problems, this research proposes the creation of a CEP system that can be offered as a service and used over the Internet. Such a CEP as a Service (CEPaaS) system would give its users CEP functionalities associated with the advantages of the services model, such as no up-front investment and low maintenance cost. Nevertheless, creating such a service involves challenges that are not addressed by current CEP systems. This research proposes solutions for three open problems that exist in this context. First, to address the problem of understanding and reusing existing CEP management procedures, this research introduces the Attributed Graph Rewriting for Complex Event Processing Management (AGeCEP) formalism as a technology- and language-agnostic representation of queries and their reconfigurations. Second, to address the problem of evaluating CEP query management and processing strategies, this research introduces CEPSim, a simulator of cloud-based CEP systems. Finally, this research also introduces a CEPaaS system based on a multi-cloud architecture, container management systems, and an AGeCEP-based multi-tenant design. To demonstrate its feasibility, AGeCEP was used to design an autonomic manager and a selected set of self-management policies. Moreover, CEPSim was thoroughly evaluated by experiments that showed it can simulate existing systems with accuracy and low execution overhead. Finally, additional experiments validated the CEPaaS system and demonstrated it achieves the goal of offering CEP functionalities as a scalable and fault-tolerant service. In tandem, these results confirm this research significantly advances the CEP state of the art and provides novel tools and methodologies that can be applied to CEP researchDoutoradoCiência da ComputaçãoDoutor em Ciência da Computação140920/2012-9CNP

Fundamental Approaches to Software Engineering

computer software maintenance; computer software selection and evaluation; formal logic; formal methods; formal specification; programming languages; semantics; software engineering; specifications; verificatio