Várias pesquisas têm sido conduzidas no contexto de ensino e treinamento, sendo o desenvolvimento de módulos educacionais uma das atividades relevantes investigada. Neste trabalho são discutidos e estabelecidos mecanismos de apoio à atividade de modelagem de conteúdos e ao processo de desenvolvimento de tais módulos. Requisitos e perspectivas para a modelagem conceitual, instrucional e didática são identificadas. Uma abordagem integrada (AIM-CID) envolvendo diferentes aspectos associados à modelagem de conteúdos também é proposta. No nível conceitual, mapas conceituais estendidos são utilizados. No nível instrucional, é estabelecido o modelo HMBS/Instrucional. No nível didático, propõe-se o modelo HMBS/Didático. Quanto ao processo de desenvolvimento, atividades e tarefas sistemáticas são estabelecidas no contexto de um processo padrão para a elaboração de módulos educacionais. Investigam-se ainda aspectos associados às atividades de especialização e instanciação do processo padrão definido. Um modelo de maturidade de processos - CMM/Educacional - é proposto. Além disso, uma instância do processo padrão definido é aplicada no desenvolvimento de um módulo educacional no domínio de Teste de Software / Many research have been conducted regarding to education and learning. In this context, one of the relevant activities is the development of educational modules. In this work, we have discussed and investigated mechanisms to support the content modelling activity and the development process of such modules. Requirements and perspectives for conceptual, instructional and didactic modelling are identified. An integrated approach (IMA-CID) dealing with different perspectives related to the modelling content activity is also proposed. In the conceptual level, extended conceptual maps are applied. In the instructional level, the HMBS/Instructional model is established. In the didactic level, the HMBS/Didactic model is proposed. Regarding to the development process, systematic activities and tasks are established in the context of a standard process for the development of educational modules. Specialization and instantiation activities are also investigated. A maturity model - CMM/Educational - is proposed. Also, an instance of the defined standard process is applied on the development of an educational module for Software Testing knowledge domain

Este trabalho investiga a aplicação de critérios de teste para o teste de especificações do aspecto comportamental de Sistemas Reativos, descritos em Estelle e em Statecharts. A utilização de Sistemas Reativos em várias atividades humanas, requer uma maior qualidade tanto do produto como do processo de desenvolvimento, pois falhas nesses sistemas podem ocasionar riscos para vidas humanas e perdas econômicas. Os critérios de teste propostos nesta tese visam a fornecer uma medida de cobertura dos testes, permitindo que a qualidade da atividade de teste possa ser mensurada e avaliada. Esta tese apresenta contribuições para as três atividades fundamentais no contexto de teste de software, que são: definição de critérios de teste, desenvolvimento de estudos teóricos/empíricos e desenvolvimento de ferramentas. Com relação à definição de critérios de teste, é proposta a aplicação do Teste de Mutação para Estelle e a aplicação de critérios de Fluxo de Controle para Estelle e Statecharts. Para o Teste de Mutação, são identificados os tipos de erros em especificações Estelle, definidos os operadores de mutação, estratégias de teste incrementais e critérios de mutação alternativa que visam a diminuir o custo de aplicação desse critério. Para os critérios de Fluxo de Controle, foram definidas duas famílias de critérios: FCCS - Família de Critérios de Cobertura para Statecharts e FCCE - Família de Critérios de Cobertura para Estelle. Estudos teóricos são realizados visando a analisar a complexidade do Teste de Mutação para Estelle e a relação de inclusão dos critérios FCCS e FCCE. Estudos empíricos são realizados visando a comparar os critérios de teste definidos e a analisar a sua aplicação durante a simulação de especificações Estelle e Statecharts. Com relação ao desenvolvimento de ferramentas, a família de ferramentas Proteum, que apóia a aplicação do teste de Mutação, e os ambientes para simulação de especificações Estelle (EDT) e Statecharts (StaSim) fornecem uma base essencial para o desenvolvimento das ferramentas. São apresentadas algumas ponderações que devem ser consideradas para a definição de ferramentas de apoio à aplicação dos critérios propostos. / Reactive Systems are applied to several human activities and as failures in these systems may cause human or economical losses, it is required the use of high-quality software development processes that would lead to the production of high-quality products. This thesis investigates criteria for testing of Reactive Systems\' behavior specifications, specified either in Estelle or in Statecharts. These criteria systematize the testing activity and provide mechanisms for the software tests quality assessment. This thesis presents contributions to the three fundamental activities in the context of software testing, which are: definition of testing criteria, theoretical studies and tool development. In relation to the definition of testing criteria, it is proposed the use of Mutation Testing for Estelle specifications and the use of Control Flow Testing for Estelle and Statecharts specifications. For Mutation Testing, the errors types in Estelle specifications are identified; mutation operators are defined and incremental testing strategies are established. In this context, it is explored the alternative mutation criteria, which aim at reducing the cost of application of the Mutation Testing. For Control Flow Testing, two families of criteria are defined: SCCF - Statechart Coverage Criteria Family and ECCF - Estelle Coverage Criteria Family. Theoretical studies are accomplished to analyze the complexity of the Mutation Testing to Estelle and the inclusion relation for the FCCS and FCCE criteria. Case studies are conducted to evaluate the testing criteria defined in this thesis. The application of these criteria during the simulation of Estelle and Statecharts specifications is analyzed. The Proteum family tools, that support the application of Mutation Testing, and the simulation environments to Estelle (EDT) and Statecharts (StatSim) supply an essential base for tools development. Considerations about the definition of supporting tools to the application of the proposed criteria are realized.

Embedded systems are present in many fields of application where failure may be critical. Such systems often possess characteristics that hampers the testing activity, as large amount of produced data and temporal requirements which must be specified and evaluated. There are tools that support the development of models for analysis and simulation still in the design stage. After being evaluated, a model may be used as basis to the implementation. In this case, it is important to ensure that the model is consistent with the specification. Otherwise, a divergence will be propagated to the final code. Therefore, the model must be tested prior to the codification. Simulink is a standard development and simulation tool for models of embedded systems. Its wide application in the industry has promoted the creation of free-software alternatives, as XCos. In the literature, there are researches which seek to improve the testing activity for Simulink-like models. The proposed solutions usually focus on test case selection strategies. However, little efforts have been directed to the oracle problem, that is, the difficulty in evaluating if an execution agrees with the specification. The objective of this doctorate proposal is to provide an oracle generation approach for Simulink-like models which addresses the characteristics previously summarized. Specifically, it is proposed a process, methods, procedures and a tool that enable the partially-automated generation of oracles for such models. As a main contribution, it is expected an improvement in the evaluation process of embedded systems in terms of quality, cost and time / Sistemas embarcados estão presentes em diversas áreas de aplicação em que falhas podem ser críticas. Tais sistemas frequentemente possuem características que tornam a fase de teste particularmente desafiadora, como a produção de grande quantidade de dados e requisitos temporais que precisam ser validados de acordo com a especificação. Existem ferramentas que auxiliam no desenvolvimento de modelos para análise e simulação do comportamento de sistemas embarcados ainda na fase de design. Após ser avaliado, o modelo pode ser usado como base para a implementação. Neste caso, deve-se buscar garantir que um modelo esteja de acordo com a especificação. Do contrário, tal divergência será propagada para a implementação. Portanto, e importante que o modelo seja testado antes da fase de implementação. Simulink e uma ferramenta-padrão de desenvolvimento e simulação de modelos de sistemas embarcados. Sua ampla aplicação na indústria incentivou a criação de alternativas de software livres como XCos. Na literatura, existem pesquisas que visam a aprimorar a atividade de teste de modelos Simulink-like. As soluções propostas geralmente focam em estratégias de seleção de casos de teste. Mas pouco esforço tem sido direcionado ao problema do oráculo, isto e, na dificuldade em avaliar se a execução está de acordo com a especificação. O objetivo desta proposta de doutorado é prover uma abordagem de geração de oráculos de teste para modelos simulink-like que contemple as características previamente resumidas. Especificamente, é proposto um processo, métodos, procedimentos e uma ferramenta que viabilizem a geração parcialmente automatizada de oráculos de teste para modelos Simulink-like. Como contribuição principal, é esperada a melhora da qualidade, custo e tempo do processo de validação de sistemas embarcados suportados por modelagem em Simulink e ferramentas similares

Les Components-Off-The-Shelf (COTS) sont utilisés pour le développement rapide et efficace de logiciels tout en limitant le coût. Il est important de tester le fonctionnement des composants dans le nouvel environnement. Pour les logiciels tiers,le code source des composants, les spécifications et les modèles complets ne sont pas disponibles. Dans la littérature de tels systèmes sont appelés composants “boîte noire”. Nous pouvons vérifier leur fonctionnement avec des tests en boîte noire tels que le test de non-régression, le test aléatoire ou le test à partir de modèles. Pour ce dernier, un modèle qui représente le comportement attendu du système sous test(SUT) est nécessaire. Ce modèle contient un ensemble d’entrées, le comportement du SUT après stimulation par ces entrées et l’état dans lequel le système se trouve.Pour les systèmes en boîte noire, les modèles peuvent être extraits à partir des traces d’exécutions, des caractéristiques disponibles ou encore des connaissances des experts. Ces modèles permettent ensuite d’orienter le test de ces systèmes.Les techniques d’inférence de modèles permettent d’extraire une information structurelle et comportementale d’une application et de la présenter sous forme d’un modèle formel. Le modèle abstrait appris est donc cohérent avec le comportement du logiciel. Cependant, les modèles appris sont rarement complets et il est difficile de calculer le nombre de tests nécessaires pour apprendre de façon complète et précise un modèle.Cette thèse propose une analyse et des améliorations de la version Mealy de l’algorithme d’inférence L* [Angluin 87]. Elle vise à réduire le nombre de tests nécessaires pour apprendre des modèles. La version Mealy de L* nécessite d’utiliser deux types de test. Le premier type consiste à construire les modèles à partir des sorties du système, tandis que le second est utilisé pour tester l’exactitude des modèles obtenus. L’algorithme utilise ce que l’on appelle une table d’observation pour enregistrer les réponses du système.Le traitement d’un contre-exemple peut exiger d’envoyer un nombre conséquent de requêtes au système. Cette thèse aborde ce problème et propose une technique qui traite les contre-exemples de façon efficace. Nous observons aussi que l’apprentissage d’un modèle ne nécessite pas de devoir remplir complètement ces tables. Nous proposons donc un algorithme d’apprentissage qui évite de demander ces requêtes superflues.Dans certains cas, pour apprendre un modèle, la recherche de contre-exemples peut coûter cher. Nous proposons une méthode qui apprend des modèles sans demander et traiter des contre-exemples. Cela peut ajouter de nombreuses colonnes à la table d’observation mais au final, nous n’avons pas besoin d’envoyer toutes les requêtes. Cette technique ne demande que les requêtes nécessaires.Ces contributions réduisent le nombre de tests nécessaires pour apprendre des modèles de logiciels, améliorant ainsi la complexité dans le pire cas. Nous présentons les extensions que nous avons apportées à l’outil RALT pour mettre en oeuvre ces algorithmes. Elles sont ensuite validées avec des exemples tels que les tampons, les distributeurs automatiques, les protocoles d’exclusion mutuelle et les planificateurs. / Components-Off-The-Shelf (COTS) are used for rapid and cost effective developmentof software systems. It is important to test the correct functioning of COTS in new environment. For third party software components source code, completes pecifications and models are not available. In literature such systems are referred as black box software components. Their proper functioning in new environment can be tested with black box testing techniques like, comparison testing, fuzz testing, Model based testing. For Model based software testing, software models are required, which represent the desired behavior of a system under test (SUT). A software model shows that a certain set of inputs are applicable to the SUT and how it behaves when these inputs are applied under different circumstances. For software black box systems, models can be learned from behavioral traces, available specifications, knowledge of experts and other such sources. The software models steer the testing of software systems. The model inference algorithms extractstructural and design information of a software system and present it as a formal model. The learned abstract software model is consistent with the behavior of the particular software system. However, the learned models are rarely complete and it is difficult to calculate the number of tests required to learn precise and complete model of a software system. The thesis provides analysis and improvements on the Mealy adaptation of the model inference algorithm L* [Angluin 87]. It targets at reducing the number oftests required to learn models of software systems. The Mealy adaptation of thealgorithm L* requires learning models by asking two types of tests. First type oftests are asked to construct models i.e. output queries, whereas the second type is used to test the correctness of these models i.e. counterexamples. The algorithm uses an observation table to record the answers of output queries. Processing a counterexample may require a lot of output queries. The thesis addresses this problem and proposes a technique which processes the counterexamples efficiently. We observe that while learning the models of software systems asking output queries for all of the observation table rows and columns is not required. We propose a learning algorithm that avoids asking output queries for such observationtable rows and columns. In some cases to learn a software model, searching for counterexamples may govery expensive. We have presented a technique which learns the software models without asking and processing counterexamples. But this may add many columns to the observation table and in reality we may not require to ask output queries for all of the table cells. This technique asks output queries by targeting to avoid asking output queries for such cells. These contributions reduce the number of tests required to learn software models, thus improving the worst case learning complexity. We present the tool RALT which implements our techniques and the techniques are validated by inferring the examples like buffers, vending machines, mutual exclusion protocols and schedulers.

This thesis presents an extensive survey of 100,000 websites as the basis for understanding the deployment of cookies across the Internet. The survey indicates cookie deployment on the Internet is approaching universal levels. The survey identifies the presence of P3P policies and dynamic web technologies as major predictors of cookie usage, and a number of significant relationships are established between the origin of the web application and cookie deployment. Large associations are identified between third-party persistent cookie usage and a countrys e-business environment. Cookie collection testing (CCT), a strategy for testing web applications, is presented. Cookies maintained in a browser are explored in light of anti random testing techniques, culminating in the definition of seeding vectors as the basis for a scalable test suite. Essentially CCT seeks to verify web application robustness against the modificationintentional or otherwiseof an application's internal state variables. Automation of CCT is outlined through the definition of test oracles and evaluation criterion. Evolutionary adaptive random (eAR) testing is proposed for application to the cookie collection testing strategy. A simulation study is undertaken to evaluate eAR against the current state-of-the-art in adaptive random testingfixed size candidate set, restricted random testing, quasi-random testing, and random testing. eAR is demonstrated to be superior to the other techniques for block pattern simulations. For fault patterns of increased complexity, eAR is shown to be comparable to the other methods. An empirical investigation of CCT is undertaken. CCT is demonstrated to reveal defects within web applications, and is found to have a substantial fault-triggering rate. Furthermore, CCT is demonstrated to interact with the underlying application, not just the technological platform upon which an application is implemented. Both seeding and generated vectors are found to be useful in triggering defects. A synergetic relationship is found to exist between the seeding and generated vectors with respect to distinct fault detection. Finally, a large significant relationship is established between structural and content similarity measures of web application responses, with a composite of the two similarity measures observed to be superior in the detection of faults. / Software Engineering and Intelligent Systems

Recently, covering arrays have been the subject of considerable research attention as they hold both theoretical interest and practical importance due to their applications to testing. In this thesis, we perform the first comprehensive study of a generalization of covering arrays called variable strength covering arrays, where we dictate the interactions to be covered in the array by modeling them as facets of an abstract simplicial complex. We outline the necessary background in the theory of hypergraphs, combinatorial testing, and design theory that is relevant to the study of variable strength covering arrays. We then approach questions that arise in variable strength covering arrays in a number of ways. We demonstrate their connections to hypergraph homomorphisms, and explore the properties of a particular family of abstract simplicial complexes, the qualitative independence hypergraphs. These hypergraphs are tightly linked to variable strength covering arrays, and we determine and identify several of their important properties and subhypergraphs. We give a detailed study of constructions for variable strength covering arrays, and provide several operations and divide-and-conquer techniques that can be used in building them. In addition, we give a construction using linear feedback shift registers from primitive polynomials of degree 3 over arbitrary finite fields to find variable strength covering arrays, which we extend to strength-3 covering arrays whose sizes are smaller than many of the best known sizes of covering arrays. We then give an algorithm for creating variable strength covering arrays over arbitrary abstract simplicial complexes, which builds the arrays one row at a time, using a density concept to guarantee that the size of the resultant array is asymptotic in the logarithm of the number of facets in the abstact simplicial complex. This algorithm is of immediate practical importance, as it can be used to create test suites for combinatorial testing. Finally, we use the Lovasz Local Lemma to nonconstructively determine upper bounds on the sizes of arrays for a number of different families of hypergraphs. We lay out a framework that can be used for many hypergraphs, and then discuss possible strategies that can be taken in asymmetric problems.

The overall goal of this research is to reduce the cost of software development and improve the quality of software. Symbolic execution is a program-analysis technique that is used to address several problems that arise in developing high-quality software. Despite the fact that the symbolic execution technique is well understood, and performing symbolic execution on simple programs is straightforward, it is still not possible to apply the technique to the general class of large, real-world software. A symbolic-execution system can be effectively applied to large, real-world software if it has at least the two features: efficiency and automation. However, efficient and automatic symbolic execution of real-world programs is a lofty goal because of both theoretical and practical reasons. Theoretically, achieving this goal requires solving an intractable problem (i.e., solving constraints). Practically, achieving this goal requires overwhelming effort to implement a symbolic-execution system that can precisely and automatically symbolically execute real-world programs. This research makes three major contributions. 1. Three new techniques that address three important problems of symbolic execution. Compared to existing techniques, the new techniques * reduce the manual effort that may be required to symbolically execute those programs that either generate complex constraints or parts of which cannot be symbolically executed due to limitations of a symbolic-execution system. * improve the usefulness of symbolic execution (e.g., expose more bugs in a program) by enabling discovery of more feasible paths within a given time budget. 2. A novel approach that uses symbolic execution to generate test inputs for Apps that run on modern mobile devices such as smartphones and tablets. 3. Implementations of the above techniques and empirical results obtained from applying those techniques to real-world programs that demonstrate their effectiveness.

Automated software test execution is a critical part of the modern software development process, where rapid feedback on the product quality is expected. It is of high importance that impediments related to test execution automation are prevented and removed as quickly as possible. An enabling factor for all types of improvement is to understand the nature of what is to be improved. The goal with this thesis is to further the knowledge about common problems encountered by software developers using test execution automation, in order to enable improvement of test execution automation in industrial software development. The research has been performed through industrial case studies and literature reviews. The analysis of the data have primarily been performed using qualitative methods, searching for patterns, themes, and concepts in the data.  Our main findings include: (a) a comprehensive list of potential impediments reported in the published body of knowledge on test execution automation, (b) an in-depth analysis of how such impediments may affect the performance of a development team, and (c) a proposal for a qualitative model of interactions between the main groups of phenomena that contribute to the formation of impediments in a test execution automation project. In addition to this, we contribute qualitative and quantitative empirical data from our industrial case studies.  Through our results, we find that test execution automation is a commonly under-estimated activity,  not only in terms of resources but also in terms of the complexity of the work. There is a clear tendency to perform the work ad hoc, down-prioritize the automation in favor of other activities,  and ignore the long-term effects in favor of short-term gains. This is both a technical and a cultural problem that need to be managed by awareness of the problems that may arise, and also have to be solved in the long term through education and information. We conclude by proposing a theoretical model of the socio-technical system that needs to be managed to be successful with test execution automation. / Syftet med denna avhandling är att utöka den vetenskapliga kunskapen om problem som kan uppstå under användning av automatiserad testning i industriell programvaruutveckling. Utveckling av programvara består principiellt av ett antal processteg: kravbehandling, detaljerad systemkonstruktion, implementation i form av programmering, och slutligen testning som säkerställer att kvaliteten på programvaran är tillräcklig för dess tilltänkta användare. Testning representerar en stor del av tiden och kostnaden för utveckling av programvaran, och detta gör att det är attraktivt att automatisera testningen. Automatiserade tester kan bidra med många positiva effekter. Testning som utförs om och om igen, för att säkerställa att gammal funktionalitet inte slutar att fungera när ändringar görs i programvaran, kan med fördel göras automatiserat. Detta frigör kvalificerad personal till kvalificerat arbete. Automatisering kan även minska ledtiden för testningen och därmed möjliggöra snabbare leveranser till kund. Ett annat mål med testautomatisering är att vara säker på att samma tester utförs på ett likartat sätt varje gång produkten testas, så att den håller en jämn och stabil kvalitetsnivå. Automatiserad testning är dock en mer komplex och kostsam verksamhet än vad man kan tro, och problem som uppstår under dess användning kan ha stora konsekvenser. Detta gäller i ännu större utsträckning i organisationer som använder moderna utvecklingsmetoder där automatisering är grundstenen för en effektiv kvalitetskontroll. För att kunna undvika så många problem som möjligt, är det därför mycket viktigt att förstå vad som händer när man använder testautomatisering i stor skala. Denna avhandling presenterar resultat från fallstudier i svensk industri, som, kombinerat med en systematisk genomgång av befintlig forskning inom området, har utförts för att söka djupare kunskap och möjligheter till generalisering. Arbetet har varit beskrivande, och förklarande, och bygger på empirisk forskningsmetodik.  I avhandlingen bidrar vi med (a) information om de problem relaterade till automatiserad testning som vi har identifierat i de empiriska fallstudierna, (b) en diskussion av dessa problem i relation till andra studier i området, (c) en systematisk litteraturstudie som ger en översikt över relevanta publikationer i området, (d) en analys av bevisen som insamlats genom litteraturstudien, samt (e) en modell av det organisatoriska och tekniska system som måste hanteras för att man skall nå framgång med ett testautomatiseringsprojekt. Resultaten tyder på att rent tekniska problem inte utgör huvuddelen av de problem som upplevs med testautomatisering. Istället handlar det till stora delar om organisationell dynamik: hantering av förändringen det innebär att införa automatisering, planering av automatisering och dess användning, samt vilka finansiella förväntningar man har på automatiseringen. / ITS-EASY Post Graduate School for Embedded Software and Systems

Šiame dokumente aprašytas darbas susideda iš trijų pagrindinių dalių. Pirmojoje (analizės) dalyje yra apžvelgiamos programinės įrangos kokybės užtikrinimo veiklos – konkrečiai testavimo procesas. Didžiausias dėmesys yra skiriamas automatizuotam testų generavimui. Antrojoje (projektinėje) dalyje aprašomas simboliniu vykdymu grindžiamas mutacinis testų generavimo metodas. Taip pat detalizuojamas jo realizavimas kuriamoje sistemoje – aprašomi statiniai ir dinaminiai vaizdai. Trečiojoje dalyje (tyrimo ir eksperimentinėje) yra analizuojamas sukurtas metodas, vertinamos įvairiausios jo charakteristikos, metrikos ir realizuojami patobulinimai. Šie sistemos priežiūros darbai leido sumažinti ciklomatinį metodų sudėtingumą ir pagreitinti realizuoto testų generavimo metodo veikimą. Aprašytas metodas pasižymi tuo, jog jo pagalba galima sugeneruoti testus aptinkančius programinio kodo mutacijas, o testų generavimui yra naudojamas simbolinis vykdymas, o ne atsitiktinių skaičių generatorius. / This work consists of three major parts. The first (analytical) part is the review of software quality assurance activities - specifically the testing process. The main focus is on automated test generation. The second (design) part describes the mutation testing based on symbolic execution test generation method. It also specifies the implementation details of the systems under development - described in the static and dynamic perspectives. The third part (research and experimental) is devoted for analysis of developed method. Here wide range of characteristics and metrics are analyzed. Also, some improvements are implemented. This helped to reduce system’s methods cyclomatic complexity and greatly increased speeds at witch tests generation are performed. The method described is characterized by the fact that it can help generate tests that detect mutations in the software code and symbolic execution is used for test generation, rather than a random number generator.

Code faults can seriously degrade scientific software accuracy. Therefore, it is imperative that scientific software developers scrutinize their codes in an attempt to find these faults. This thesis explores, particularly, the efficacy of code testing as a method of scientific software code fault detection. Software engineers, as experts in code quality, have developed many code testing techniques, but many of these techniques cannot readily be applied to scientific codes for at least two reasons. First, scientific software testers do not usually have access to an ideal oracle. Second, scientific software outputs, by nature, can only be judged for accuracy and not correctness. Testing techniques developed under the assumption that these two problems can be ignored--as most have been--are of questionable value to computational scientists. To demonstrate the reality of these problems and to provide an example of how software engineers and scientists can begin to address them, this thesis discusses the development and application of a novel technique: Mutation Sensitivity Testing (MST). MST is based on traditional mutation testing, but--in place of a focus on mutant "killing"--MST focuses on assessing the mutation sensitivity of a test set. In this thesis, MST experiments are conducted using eight small numerical routines, four classes of mutation operators, and 1155 tests. The results are discussed and some conclusions are drawn. Two observations are of particular interest to computational scientists. First, it is found that oracles that exhibit uncertainties greater than (approximately) 80% of the expected output are of questionable value when they are used in the testing of scientific software. Second, it is found that a small number of carefully selected tests may be sufficient to falsify a code. / Thesis (Master, Computing) -- Queen's University, 2009-04-19 13:34:08.943