<p>In this study I have looked at social impacts of mobile telephone usage in Sweden in the Spring of 2001. Through observations and interviews have I tried to outline how social relations and concepts of time have changed and are still in a process of change alongside with the high percentage of mobile phone users today.</p><p>The conclusions I have made from my research is that mobile phone usage affects society and how people interact and that people want to reach others, but want to control their own reachability. Communication via mobile phone differs from face-to-face communication and communication on stationary phones, but mobile phones seem to be used as means to facilitate face-to-face interaction. There seem to be some commonly shared notions among my informants of what appropriate mobile phone behavior is, but people seem to not always abide to this. People tend to create their own private zones in public places when using their mobile phones and through their usage send social messages to others. I have also found that the use of time is an important aspect connected to mobile phones. People seem not to make as many plans ahead any longer, but instead make up plans as they go. Many seem to have forgotten how life was before there where mobile phones!</p>

In this study I have looked at social impacts of mobile telephone usage in Sweden in the Spring of 2001. Through observations and interviews have I tried to outline how social relations and concepts of time have changed and are still in a process of change alongside with the high percentage of mobile phone users today. The conclusions I have made from my research is that mobile phone usage affects society and how people interact and that people want to reach others, but want to control their own reachability. Communication via mobile phone differs from face-to-face communication and communication on stationary phones, but mobile phones seem to be used as means to facilitate face-to-face interaction. There seem to be some commonly shared notions among my informants of what appropriate mobile phone behavior is, but people seem to not always abide to this. People tend to create their own private zones in public places when using their mobile phones and through their usage send social messages to others. I have also found that the use of time is an important aspect connected to mobile phones. People seem not to make as many plans ahead any longer, but instead make up plans as they go. Many seem to have forgotten how life was before there where mobile phones!

This thesis investigates a method for tackling the verification of parametric systems, systems whose behaviour may depend on the value of one or more parameters. The range of allowable values for such parameters may, in general, be large or unknown. This results in a large number of instances of a system that require verification, one instance for each allowable combination of parameter values. When one or more parameters are unbounded, the family of systems that require verification becomes infinite. Computer protocols are one example of such parametric systems. They may have parameters such as the maximum sequence number or the maximum number of retransmissions. Traditional protocol verification approaches usually only analyse and verify properties of a parametric system for a small range of parameter values. It is impossible to verify in this way every concrete instance of an infinite family of systems. Also, the number of reachable states tends to increase dramatically with increasing parameter values, and thus the well known state explosion phenomenon also limits the range of parameters for which the system can be analysed. In this thesis, we concentrate on the parametric verification of the Stop-and-Wait Protocol (SWP), an elementary flow control protocol. We have used Coloured Petri Nets (CPNs) to model the SWP, operating over an in-order but lossy medium, with two unbounded parameters: the maximum sequence number; and the maximum number of retransmissions. A novel method has been used for symbolically representing the parametric reachability graph of our parametric SWP CPN model. This parametric reachability graph captures exactly the infinite family of reachability graphs resulting from the infinite family of SWP CPNs. The parametric reachability graph is represented symbolically as a set of closed-form algebraic expressions for the nodes and arcs of the reachability graph, expressed in terms of the two parameters. By analysing the reachability graphs of the SWP CPN model for small parameter values, structural regularities in the reachability graphs were identified and exploited to develop the appropriate algebraic expressions for the parametric reachability graph. These expressions can be analysed and manipulated directly, thus the properties that are verified from these expressions are verified for all instances of the system. Several properties of the SWP that are able to be verified directly from the parametric reachability graph have been identified. These include a proof of the size of the parametric reachability graph in terms of both parameters, absence of deadlocks (undesired terminal states), absence of livelocks (undesirable cycles of behaviour from which the protocol cannot escape), absence of dead transitions (actions that can never occur) and the upper bounds on the content of the underlying communication channel. These are verified from the algebraic expressions and thus hold for all parameter values. Significantly, language analysis is also carried out on the parametric SWP. The parametric reachability graph is translated into a parametric Finite State Automaton (FSA), capturing symbolically the infinite set of protocol languages (i.e. sequences of user observable events) by means of similar algebraic expressions to those of the parametric reachability graph. Standard FSA reduction techniques were applied in a symbolic fashion directly to the parametric FSA, firstly to obtain a deterministic representation of the parametric FSA, then to obtain an equivalent minimised FSA. It was found that the determinisation procedure removed the effect of the maximum number of retransmissions parameter, and the minimisation procedure removed the effect of the maximum sequence number parameter. Conformance of all instances of the SWP over both parameters to its desired service language is proved. The development of algebraic expressions to represent the infinite class of Stop-and-Wait Protocols, and the verification of properties (including language analysis) directly from these algebraic expressions, has demonstrated the potential of this method for the verification of more general parametric systems. This thesis provides a significant contribution toward the development of a general parametric verification methodology.

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Il s'agit d'une étude menée sur les systèmes cyber-physiques sur trois aspects principaux: la vérification de la stabilité, l'ordonnancement et la synthèse des paramètres. Les systèmes de contrôle embarqués (ECS) agissant dans le cadre de contrats temporels sont la classe considérée de systèmes cyber-physiques dans la thèse. ECS fait référence à des intégrations d'un dispositif informatique avec le système physique. En ce qui concerne les contrats temporels, ils sont des contraintes de temps sur les instants où se produisent certains événements tels que l'échantillonnage, l'actionnement et le calcul. Ces contrats sont utilisés pour modéliser les problèmes qui se posent dans les systèmes de contrôle modernes: incertitudes sur les retards d'actionnement, les périodes d'échantillonnage incertaines et l'interaction de plusieurs systèmes physiques avec des ressources informatiques partagées (CPUs). Maintenant, compte tenu d'un ECS et d'un contrat temporel, nous reformulons le système de manière impulsionnelle et vérifions la stabilité du système, sous toutes les incertitudes bornées et données par le contrat, en utilisant des techniques d'approximation convexe et de nouveaux résultats généralisés pour le problème sur une classe de systèmes modélisés dans le cadre des inclusions différentielles. Deuxièmement, compte tenu d'un ensemble de contrôleurs implémentés sur une plate-forme de calcul commune (CPUs), dont chacun est soumis à un contrat de synchronisation, et à son meilleur et son plus mauvais cas d'exécution dans chaque CPU, nous synthétisons une politique d’ordonnancement dynamique qui garantit que chaque contrat temporel est satisfait et que chacun des CPU partagés est attribué à au plus un contrôleur à tout moment. L'approche est basée sur une reformulation qui nous permet d'écrire le problème d’ordonnancement comme un jeu temporelle avec spécification de sureté. Ensuite, en utilisant l'outil UPPAAL-TIGA, une solution au jeu fournit une politique d’ordonnancement appropriée. En outre, nous fournissons une nouvelle condition nécessaire et suffisante pour l’ordonnancement des tâches de contrôle en fonction d’un jeu temporisé simplifiés. Enfin, nous résolvons un problème de synthèse de paramètres qui consiste à synthétiser une sous-approximation de l'ensemble des contrats de synchronisation qui garantissent en même temps l’ordonnancement et la stabilité des contrôleurs intégrés. La synthèse est basée sur un nouveau paramétrage du contrat temporel pour les rendre monotones, puis sur un échantillonnage à plusieurs reprises de l'espace des paramètres jusqu'à atteindre une précision d'approximation prédéfinie. / This is a study conducted on cyber-physical systems on three main aspects: stability verification, scheduling, and parameter synthesis. Embedded control systems (ECS) acting under timing contracts are the considered class of cyber-physical systems in the thesis. ECS refers to integrations of a computing device with the physical system. As for timing contracts they are time constraints on the instants where some events happen such as sampling, actuation, and computation. These contracts are used to model issues that arise in modern embedded control systems: uncertain sampling to actuation delays, uncertain sampling periods, and interaction of several physical systems with shared computational resources (CPUs). Now given an ECS and a timing contract we reformulate the system into an impulsive one and verifies stability of the system, under all possible bounded uncertainties given by the contract, using safe convex approximation techniques and new generalized results for the problem on a class of systems modeled in the framework of difference inclusions. Second given a set of controllers implemented on a common computational platform (CPUs), each of which is subject to a timing contract, and best and worst case execution times on each CPU, we synthesize a dynamic scheduling policy, which guarantees that each timing contract is satisfied and that each of the shared CPUs are allocated to at most one embedded controller at any time. The approach is based on a timed game formulation that allows us to write the scheduling problem as a timed safety game. Then using the tool UPPAAL-TIGA, a solution to the safety game provides a suitable scheduling policy. In addition, we provide a novel necessary and sufficient condition for schedulability of the control tasks based on a simplified timed game automaton. Last, we solve a parameter synthesis problem which consists of synthesizing an under-approximation of the set of timing contracts that guarantee at the same time the schedulability and stability of the embedded controllers. The synthesis is based on a re-parameterization of the timing contract to make them monotonic, and then on a repeatedly sampling of the parameter space until reaching a predefined precision of approximation.

Les programmes informatiques prennent une place de plus en plus importante dans nos vies. Certains de ces programmes, comme par exemple les systèmes de contrôle de centrales électriques, d'avions ou de systèmes médicaux sont critiques : une panne ou un dysfonctionnement pourraient causer la perte de vies humaines ou des dommages matériels ou environnementaux importants. Les méthodes formelles visent à offrir des moyens de concevoir et vérifier de tels systèmes afin de garantir qu'ils fonctionneront comme prévu. Au fil du temps, ces systèmes deviennent de plus en plus évolués et complexes, ce qui est source de nouveaux défis pour leur vérification. Il devient nécessaire de développer ces systèmes de manière modulaire afin de pouvoir distribuer la tâche d'implémentation à différentes équipes d'ingénieurs. De plus, il est important de pouvoir réutiliser des éléments certifiés et les adapter pour répondre à de nouveaux besoins. Aussi les méthodes formelles doivent évoluer afin de s'adapter à la conception et à la vérification de ces systèmes modulaires de taille toujours croissante. Nous travaillons sur une approche algébrique pour la conception de systèmes corrects par construction. Elle définit un formalisme pour exprimer des spécifications de haut niveau et permet de les raffiner de manière incrémentale en des spécifications plus concrètes tout en préservant leurs propriétés, jusqu'à ce qu'une implémentation soit atteinte. Elle définit également plusieurs opérations permettant de construire des systèmes complexes à partir de composants plus simples en fusionnant différents points de vue d'un même système ou en composant plusieurs sous-systèmes ensemble, ainsi que de décomposer une spécification complexe afin de réutiliser des composants existants et de simplifier la tâche d'implémentation. Le formalisme de spécification que nous utilisons est basé sur des spécifications modales. Intuitivement, une spécification modale est un automate doté de deux types de transitions permettant d'exprimer des comportements optionnels ou obligatoires. Raffiner une spécification modale revient à décider si les parties optionnelles devraient être supprimées ou rendues obligatoires. Cette thèse contient deux principales contributions théoriques basées sur une extension des spécifications modales appelée " spécifications à ensembles d'acceptation ". La première contribution est l'identification d'une sous-classe des spécifications à ensembles d'acceptation, appelée " spécifications à ensembles d'acceptation convexes ", qui permet de définir des opérations bien plus efficaces tout en gardant un haut niveau d'expressivité. La seconde contribution est la définition d'un nouveau formalisme, appelé " spécifications à ensembles d'acceptation marquées ", qui permet d'exprimer des propriétés d'atteignabilité. Ceci peut, par exemple, être utilisé pour s'assurer qu'un système termine ou exprimer une propriété de vivacité dans un système réactif. Les opérations usuelles sont définies sur ce nouveau formalisme et elles garantissent la préservation des propriétés d'atteignabilité. Cette thèse présente également des résultats d'ordre plus pratique. Tous les résultats théoriques sur les spécifications à ensembles d'acceptation convexes ont été prouvés en utilisant l'assistant de preuves Coq. L'outil MAccS a été développé pour implémenter les formalismes et opérations présentés dans cette thèse. Il permet de les tester aisément sur des exemples, ainsi que d'étudier leur efficacité sur des cas concrets. / Software programs are taking a more and more important place in our lives. Some of these programs, like the control systems of power plants, aircraft, or medical devices for instance, are critical: a failure or malfunction could cause loss of human lives, damages to equipments, or environmental harm. Formal methods aim at offering means to design and verify such systems in order to guarantee that they will work as expected. As time passes, these systems grow in scope and size, yielding new challenges. It becomes necessary to develop these systems in a modular fashion to be able to distribute the implementation task to engineering teams. Moreover, being able to reuse some trustworthy parts of the systems and extend them to answer new needs in functionalities is increasingly required. As a consequence, formal methods also have to evolve in order to accommodate both the design and the verification of these larger, modular systems and thus address their scalability challenge. We promote an algebraic approach for the design of correct-by-construction systems. It defines a formalism to express high-level specifications of systems and allows to incrementally refine these specifications into more concrete ones while preserving their properties, until an implementation is reached. It also defines several operations allowing to assemble complex systems from simpler components, by merging several viewpoints of a specific system or composing several subsystems together, as well as decomposing a complex specification in order to reuse existing components and ease the implementation task. The specification formalism we use is based on modal specifications. In essence, a modal specification is an automaton with two kinds of transitions allowing to express mandatory and optional behaviors. Refining a modal specification amounts to deciding whether some optional parts should be removed or made mandatory. This thesis contains two main theoretical contributions, based on an extension of modal specifications called acceptance specifications. The first contribution is the identification of a subclass of acceptance specifications, called convex acceptance specifications, which allows to define much more efficient operations while maintaining a high level of expressiveness. The second contribution is the definition of a new formalism, called marked acceptance specifications, that allows to express some reachability properties. This could be used for example to ensure that a system is terminating or to express a liveness property for a reactive system. Usual operations are defined on this new formalism and guarantee the preservation of the reachability properties as well as independent implementability. This thesis also describes some more practical results. All the theoretical results on convex acceptance specifications have been proved using the Coq proof assistant. The tool MAccS has been developed to implement the formalisms and operations presented in this thesis. It allows to test them easily on some examples, as well as run some experimentations and benchmarks.

Para satisfazer o explosivo aumento na demanda de tráfego de voz e dados, as redes ópticas baseadas em WDM e GMPLS estão sendo desenvolvidas. A suíte de protocolos GMPLS é atualmente considerada como um plano de controle para as redes ópticas e é composta por protocolos de sinalização e de roteamento, como também do protocolo de gerenciamento de enlace (LMP). O LMP é um importante protocolo que interfere na atribuição de rótulos (comprimentos de onda) e é necessário fazer sua análise lógica para verificar se o mesmo está livre de erros de progresso. Para esta finalidade, o método denominado alcançabilidade justa foi utilizado. Verificada a corretude do LMP, o estudo foca o subproblema de atribuição de comprimento de onda do RWA nas redes GMPLS-WDM por ser um dos principais problemas que causam o baixo desempenho destas redes. O cenário estudado é das redes GMPLS-WDM que operam em um ambiente RWA dinâmico com restrição de continuidade de comprimento de onda. O problema RWA é examinado bem como as várias heurísticas de atribuição de comprimento de onda apresentadas na literatura. Com o objetivo de melhorar o desempenho das redes GMPLS-WDM com restrição de continuidade de comprimento de onda, propõe-se um algoritmo de atribuição de rótulos que utiliza os conceitos conjunto de rótulos e SRLG já implementados pelo GMPLS. O algoritmo proposto melhora a eficiência no uso de recursos nas redes em questão. O desempenho é verificado através da métricas de probabilidade de bloqueio de conexão, desempenho este próximo do ótimo e demonstrado através de simulações. / To satisfy the explosive increasing demands of voice and data traffic, optical networks based on WDM and GMPLS are being developed. The GMPLS´ suite of protocols is currently being considered as the control plane for optical networks and it is compounded of signaling and routing protocols, and also the link management protocol (LMP). The LMP is an important protocol that interferes with label (wavelength) assignment and it is necessary to logically analyse this protocol in order to verify if it is free from progress errors. For this purpose, the method called fair reachability has been used. Verified the LMP is correctable, the study focuses on the RWA wavelength assignment problem in GMPLS-WDM networks because it is one of the main problems which causes the low performance of these networks. The studied scene is GMPLS-WDM networks operating under a dynamic RWA environment with wavelength continuity constraint. The RWA problem is examined and also the various wavelength-assignment heuristics proposed in the literature. With the goal to improve the performance of the GMPLS-WDM networks with wavelength continuity constraint, it is proposed a label assignment algorithm, which uses the concepts of label set and SRLG, already implemented by GMPLS. The proposed algorithm provides an improvement in efficiency of resource use. The performance is verified by using the blocking probability metric, and it is very close to the optimum and demonstrated through simulations.

Neste trabalho estudamos as noções de alcançabilidade e controlabilidade para sistemas lineares a tempo contínuo com perturbações aditivas e saltos nos parâmetros sujeitos a uma cadeia de Markov geral. Definimos conceitos de alcançabilidade e controlabilidade médios de maneira natural exigindo que os valores esperados dos gramianos correspondentes sejam definidos positivos. Visando obter uma condição testável para ambos os conceitos, introduzimos conjuntos de matrizes de alcançabilidade e de controlabilidade para esta classe de sistemas e usamos certas propriedades de invariância para mostrar que: o sistema é alcançável em média, e, analogamente, controlável em média, se e somente se as matrizes respectivas, de alcançabilidade e de controlabilidade, têm posto completo. Usamos alcançabilidade média de sistemas para mostrar que a matriz de segundo momento do estado é definida positiva com uma margem uniforme. Uma consequência deste resultado no problema de estimação linear do estado é que a matriz de covariância do erro de estimação é positiva definida em média, no sentido que existe um nível mínimo de ruído nas estimativas. Na sequência, para estimadores lineares markovianos, estudamos a limitação do valor esperado da matriz de covariância do erro para mostrar que o filtro é estável num certo sentido, sendo esta uma propriedade desejável em aplicações reais. Quanto às aplicações da controlabilidade média, usamos este conceito para estabelecer condições necessárias e suficientes que garantem a existência de um processo de controle que leva a componente contínua do estado do sistema para a origem em tempo finito e com probabilidade positiva. / In this work we study the reachability and controllability notions for continuous-time linear systems with exogenous inputs and jump parameters driven by a quite general Markov chain. We define a rather natural average reachability and controllability concepts by requiring that the associated gramians are average positive definite, respectively. Aiming at testable conditions for each concept, we introduce certain sets of matrices linked with the gramians, and employ some invariance properties to find rank-based conditions. We show for average reachable systems that the state second moment is positive definite. One consequence of this result in the context of linear estimation for reachable systems is that the expectation of the error covariance matrix is positive definite. Moreover, for linear markovian filters we study the average boundedness of the error covariance matrix to show that the filter is stable in an appropriate sense, which consists in a property that is desirable in real applications. Regarding the average controllability concept, we show that it is a necessary and sufficient condition for the feasibility of the following control problem: find a control process that drives the continuous component of the state to zero in finite time with positive probability.

Este trabalho é dedicado ao estudo do erro de estimação em filtragem linear para sistemas lineares com parâmentros sujeitos a saltos markovianos a tempo discreto. Indroduzimos o conceito de alcançabilidade média para uma classe de sistemas. Construímos um conjunto de matrizes de alcançabilidade e mostramos que o conceito usual de alcan- çabilidade definido através da positividade do gramiano é caracterizado pela definição por posto completo destas matrizes. A alcançabilidade média funciona como condição necessária e suficiente para positividade do segundo momento do estado do sistema, resultado esse que auxilia na caracterização da positividade uniforme da matriz de covariância do erro de estimação. Abordamos a estabilidade de estimadores com a interpretação de que a covariância do erro permanece limitada na presença de erro de qualquer magnitude no modelo do ruído, que é uma característica relevante para aplicações. Apresentamos uma prova de que filtros markovianos são estáveis sempre que o segundo momento condicionado é positivo. Exemplos numéricos encontram-se inclusos. / This work studies linear filtering for discrete-time systems with Markov jump parameters. We introduce a notion of average reachability for these systems and present a set of matrices playing the role of reachability matrices, in the sense that their rank is full if and only if the system is average reachable. Reachability is also a sufficient condition for the second moment of the system to be positive. Uniform positiveness of the error covariance matrix is studied for general (possibly non-markovian) linear estimators, relying on the state second moment positiveness. Satbility of linear markovian estimators is also addressed, allowing to show that markovian estimators are stable whenever the system is reachable, with the interpretation that the error covariance remains bounded in the presence of error of any magnitude in the model of the noise, which is a relevant feature for applications. Numerical examples are included.

Denna studie undersöker om det är möjligt att införa nåbarhetstestning i en baneditor. Testets syfte är att ersätta manuell testing, det vill säga att bankonstruktören inte ska behöva spela igenom banan för att säkerställa att denne kommer kunna nå alla nåbara positioner.För att kunna utföra studien skapas en enkel baneditor som testplattform. Vidare utförs en jämförande studie av flera alternativa algoritmer för att fastställa vilken som är mest passande för nåbarhetstestning i en baneditor.Resultatet från den jämförande studien visade att A* (A star) var den mest passande algoritmen för funktionen. Huruvida automatisk testning kan ersätta manuell testning är diskutabelt, men resultatet pekar på en ökad effektivitet i tid när det kommer till banbygge. / The following study examines whether it is possible to implement reachability testing in a map editor designed for 2D-platform games. The purpose of reachability testing is to replace manual testing, that being the level designer having to play through the map just to see if the player can reach all supposedly reachable positions in the map.A simple map editor is created to enable the implementation after which we perform a theoretical study in order to determine which algorithm would be best suited for the implementation of the reachability testing.The results comparing algorithms shows that A* (A star) worked best with the function. Whether or not manual testing can be replaced by automatic testing is open for debate, however the results points to an increase in time efficiency when it comes to level design.