Publish/Subscribe (in short pub/sub) allows clients that share common interest communicate in an asynchronous and loosely-coupled fashion. This paradigm is adopted by many distributed event-driven applications such as social networking services, distributed business processes and cyber-physical systems. These applications cannot afford to have the underlying pub/sub substrate perform unreliably, permanently fail or behave arbitrarily as it will cause significant disturbance to stably serving many end-users. Therefore, a research effort on making pub/sub systems resilient against various failures to sustain high quality of service to the clients is imperative. In this thesis, we focus on the overlay of pub/sub brokers that are widely adopted as a popular architecture for large-scale pub/sub systems. Broker overlays can suffer from various issues such as degradation of topology quality, brokers causing transient or permanent benign failures and Byzantine brokers behaving arbitrarily. We aim to make novel research contributions by exploring fundamental techniques that can help the broker overlays maintain functional and non-functional requirements even under the presence of the aforementioned failures and necessary administrative updates. We first build a set of overlay adaptation primitives that re-configure topologies such as shifting links and replicating brokers. These primitives are designed to involve a small local group of brokers in the pub/sub overlays so that the disruption during the execution of large-scale and dynamic changes can be controlled in a fined-grained manner. For the problem of degrading topology quality, automated planning systems are developed to find a sequence of adaptations that would cause minimal disruption to running services. Also, our primitives can be executed on demand to quickly fail-over a crashed broker or off-load congested brokers. In addition, these on-demand primitives can be used to form a group of dynamically replicated brokers that enforce a novel safety measure to prevent Byzantine brokers from sabotaging the pub/sub overlays. Our contributions are evaluated with systematic consideration of various trade-offs between functional and non-functional properties.

Techn. University, Diss., 2005--Berlin.

AbstractThis thesis is about the visual analysis of author impact and other bibliometric data such as an authorspublication history. It utilizes Publish or Perish as a data source, which is a search tool to find thisbibliometric data. Bibliometric data is a concept within Bibliometrics with which to find and definenotable publications, to draw a number of different conclusions, such as how much impact an authorhas had in a given field. To do this we use information visualization techniques. InformationVisualization is a field of science about increasing insight and understanding of raw data. It does this byresearching on details of human cognition and perception and how data itself is modeled, and bycategorizing and developing new ways to encode and interact with data visually.Since Publish or Perish only gives its information as a raw text feed, and do not allow for anyreal comparisons between authors, this thesis tries to rectify this by introducing a web basedvisualization tool to analyze this data. The data itself consists of a number of scientifically definedindexes which measures an author's impact in his given field, an overview of his publication history,and some general bibliometric data.

This thesis deals with data distribution service and is divided into three parts. The first part of this thesis focuses on theoretical knowledge of data distribution service. This section gradually introduces the model used in data distribution service, quality of service and the RTPS protocol, which was specially developed for the needs of data distribution service. The most comprehensive part of the theoretical part deals with security in data distribution service. At the end of the first part of this thesis, selected impelementations of data distribution service are introduced. The second part of this thesis deals with practical use of data distribution service, while OpenDDS implementation is chosen for the practical part. This part initially deals with the design of basic communication scenarios, followed by the design of complex communication scenarios. In the next chapters, within the practical part, the thesis is focused on verifyng security of the data distribution service selected implementation, design of security incidents and their subsequent simulation. Content of the final part of this thesis is the introduction of a tool designed for this thesis, which is used to implement selected types of attacks.

Sharing information securely between business partners and managing large supply chains effciently will be a crucial competitive advantage for enterprises in the near future. In this paper, we present a concept that allows for building value networks between business partners in a distributed manner. Companies are able to publish Linked Data which participants of the network can clone and subscribe to. Subscribers get noticed as soon as new information becomes available. This provides a technical infrastructure for business communication acts such as supply chain communication or master data management. In addition to the conceptual analysis, we provide an implementation enabling companies to create such dynamic semantic value networks.

En raison du grand succès des réseaux sociaux, la nature et mode de diffusion del’information sur le Web a changé en faveur de contenus dynamiques diffusés sousforme de flux d’information. Dans le contexte des réseaux sociaux, les utilisateurs peuvent s’abonner à de multiples sources d’information et recevoir continuellement de nouveaux contenus. Or, ce nouveau mode de publication/consommation peut entraîner d’énormes quantités d’information, en surchargeant les utilisateurs. Ainsi,il est essentiel de développer des techniques efficaces de filtrage et de classement qui permettent aux utilisateurs d’être efficacement mis à jour avec le contenu le plus intéressant.Les requêtes top-k sur les flux d’information limitent les résultats au contenu le plus pertinent. Pour améliorer la pertinence des résultats, le modèle de classement des résultats de requêtes devrait tenir compte de divers facteurs de contexte, y compris les facteurs traditionnels basés sur le contenu, les facteurs liés aux utilisateurs et leurs relations (réseau social). Dans le réseau social, le maintien des ensembles de top-k peut être plus difficile car de nombreux événements pourraient changer les messages de top-k tels que le nouveau message, la nouvelle action, le nouvel utilisateur, les modifications de profil, etc. Pour un grand réseau social avec des millions d’utilisateurs et des milliards de messages, le traitement continu des requêtes top-k est l’approche la plus efficace. Cependant, les systèmes actuels pour le traitementcontinu des requêtes top-k échouent lorseque ces systèmes considèrent des modèles de classement riches avec des critères de réseau social. En outre, de tels systèmes ne tiennent pas compte de la diversité des contenus publiés.Dans cette thèse, nous nous concentrons sur le filtrage des flux d’information basé sur le calcul des messages top-k pour chaque utilisateur dans le réseau social. Nous visons à développer un système à large échelle capable d’évaluer efficacement les requêtes top-k continues avec une fonction de classement complexe. Nous proposons l’algorithme SANTA, capable de gérer des fonctions de classement complexes avec des critères sociaux tout en maintenant un traitement continu des requêtes top-k. Nous proposons aussi une variante (SANTA +) qui accélère le traitement d’actions dans les réseaux sociaux. Pour tenire compte de la diversité des contenus publiés, nous proposons l’algorithme DA-SANTA qui étend l’algorithme SANTA pour intégrer la diversité dans le modèle top-k continu tout en maintenant l’efficacité du système. Nos expérimentation sont menées sur des données réelles extraite de Twitter, illustrant les propriétés de nos algorithmes et de montrer leur efficacité. / Information streams provide today a prevalent way of publishing and consuming content on the Web, especially due to the great success of social networks. In the social networks context, users may subscribe to several information sources of interest and continuously receive new published content. But, this new publishing/consumption mode may lead to huge amounts of received information, overwhelming for human processing. Thus, there is a vital need to develop effective filtering and ranking techniques which allow users to efficiently be updated with the most interesting content. Top-k queries over the streams of interest allow limiting results to the most relevant content. To provide a relevant content, the ranking model should consider various context factors including traditional IR factors and social network. In the social network, maintaining top-k sets may be more difficult because many events could produce changes in the top-k sets such as new message, new action, new user, profile changes, etc. For a large social network with millions of users and billionsof messages, the continuous processing of the top-k queries is the most effective approach. However, current systems fail in combining continuous top-k processing with rich scoring models including social network criteria. Moreover, such systems do not consider the diversity of published content.In this thesis, we focus on filtering information streams based on the computation of top-k messages for each user in the social network. We aim to develop a scalable system that be able to efficiently evaluate the continuous top-k queries using the continuous approach with a ranking function including social network criteria. We propose the SANTA algorithm, able to handle scoring functions including content similarity but also social network criteria and events in a continuous processing of top-k queries. We propose a variant (SANTA+) that accelerates the processing of interaction events in social networks. To provide both diverse and relevant messages in top-k sets, we propose the DA-SANTA algorithm which extends the SANTA algorithm to integrate the diversity into the continuous top-k model while maintaining the efficiency of the system. Our experiments are conducted over a real data-set extracted from Twitter, illustrating the properties of our algorithms and demonstrating their efficiency.

[pt] Esta dissertação apresenta a solução de balanceamento de carga baseada em fatias de processamento de dados (Data Processing Slice Load Balancing solution) para permitir o balanceamento de carga dinâmico do processamento de fluxos de dados em sistemas baseados em DDS (Data Distribution Service). Um grande número de aplicações requer o processamento contínuo de alto volume de dados oriundos de várias fontes distribuídas., tais como monitoramento de rede, sistemas de engenharia de tráfego, roteamento inteligente de carros em áreas metropolitanas, redes de sensores, sistemas de telecomunicações, aplicações financeiras e meteorologia. Conceito chave da solução proposta é o Data Processing Slice, o qual é a unidade básica da carga de processamento dos dados dos nós servidores em um domínio DDS. A solução consiste de um nó balanceador, o qual é responsável por monitorar a carga atual de um conjunto de nós processadores homogêneos e quando um desbalanceamento de carga é detectado, coordenar ações para redistribuir entre os nós processadores algumas fatias de carga de trabalho de forma segura. Experimentos feitos com grandes fluxos de dados que demonstram a baixa sobrecarga, o bom desempenho e a confiabilidade da solução apresentada. / [en] This thesis presents the Data Processing Slice Load Balancing solution to enable dynamic load balancing of Data Stream Processing on DDS-based systems (Data Distribution Service). A large number of applications require continuous and timely processing of high-volume of data originated from many distributed sources, such as network monitoring, traffic engineering systems, intelligent routing of cars in metropolitan areas, sensor networks, telecommunication systems, financial applications and meteorology. The key concept of the proposed solution is the Data Processing Slice (DPS), which is the basic unit of data processing load of server nodes in a DDS Domain. The Data Processing Slice Load Balancing solution consists of a load balancer, which is responsible for monitoring the current load of a set of homogenous data processing nodes and when a load unbalance is detected, it coordinates the actions to redistribute some data processing slices among the processing nodes in a secure way. Experiments with large data stream have demonstrated the low overhead, good performance and the reliability of the proposed solution.

Os avanços tecnológicos das últimas décadas têm motivado o desenvolvimento dos edifícios inteligentes, visando à criação de ambientes mais confortáveis e seguros para os ocupantes, economicamente vantajosos para os proprietários e ambientalmente corretos. Considerando-se que nestes ambientes emergem novas formas de interação entre os usuários e os sistemas prediais, as quais não são adequadamente tratadas por técnicas convencionais de modelagem, torna-se necessário o estudo de novas soluções que abordem essas interações. Assim, este trabalho apresenta a proposta de uma abordagem sistemática para modelar e simular os sistemas de controle de edifícios inteligentes. Considera-se o sistema de controle como um sistema orientado por eventos discretos, no qual a comunicação entre os dispositivos que o constituem é realizada por meio da troca assíncrona de mensagens. Nesta abordagem, é utilizada a rede de Petri colorida para especificar as funcionalidades do edifício inteligente e a interação entre os dispositivos que constituem o seu sistema de controle. Assim, fornece-se um procedimento estruturado para desenvolver modelos que facilita a especificação do algoritmo de controle dos subsistemas do edifício inteligente. Para avaliar as principais características do procedimento proposto, foi apresentado um exemplo de aplicação que aborda a integração das funcionalidades de um sistema de telefonia distribuído e um sistema de vigilância predial. A abordagem de modelagem possibilitou a identificação das funcionalidades dos dispositivos inteligentes que integram o sistema de controle em diferentes níveis de abstração e as interações que ocorrem durante o seu funcionamento. A realização deste trabalho contribui para o aprimoramento de novas abordagens para o desenvolvimento de sistemas de controle com arquiteturas heterárquicas. Estes sistemas são constituídos por dispositivos inteligentes colaborativos, que possuem um elevado grau de autonomia. / Technological advances in recent decades have motivated the development of intelligent buildings, aimed at creating environments more productive for the occupants, economically advantageous for the owners and environmentally correct. New ways of interaction between users and the buildings systems are emerging from these kinds of systems, which are not adequately treated by conventional modeling techniques. In this sense, it is necessary the study of new approaches which address these new functionalities. Thus, this work presents a proposal for a systematic approach to model and simulate the control system of the intelligent buildings. The control system is considered to be a discrete event system, where the communication between the devices that integrate it is oriented by means of asynchronous messages exchange. This approach uses the colored Petri nets in order to specify the functionalities of the building system and their devices interactions. The approach provides a structured procedure to develop models that facilitate the algorithm specification of the control system. In order to verify the main characteristics of the proposed procedure, it is presented an example that is a control system that integrates a distributed telephony system and a surveillance building system. The approach proposed enabled the identification of the main functionalities and interactions of the intelligent devices constituting the control system. The achievement of this thesis contributes to the development of new approaches to develop heterarchical control system architectures. This kind of system architectures is constituted by collaborative intelligent devices that have a high degree of autonomy.

Os avanços tecnológicos das últimas décadas têm motivado o desenvolvimento dos edifícios inteligentes, visando à criação de ambientes mais confortáveis e seguros para os ocupantes, economicamente vantajosos para os proprietários e ambientalmente corretos. Considerando-se que nestes ambientes emergem novas formas de interação entre os usuários e os sistemas prediais, as quais não são adequadamente tratadas por técnicas convencionais de modelagem, torna-se necessário o estudo de novas soluções que abordem essas interações. Assim, este trabalho apresenta a proposta de uma abordagem sistemática para modelar e simular os sistemas de controle de edifícios inteligentes. Considera-se o sistema de controle como um sistema orientado por eventos discretos, no qual a comunicação entre os dispositivos que o constituem é realizada por meio da troca assíncrona de mensagens. Nesta abordagem, é utilizada a rede de Petri colorida para especificar as funcionalidades do edifício inteligente e a interação entre os dispositivos que constituem o seu sistema de controle. Assim, fornece-se um procedimento estruturado para desenvolver modelos que facilita a especificação do algoritmo de controle dos subsistemas do edifício inteligente. Para avaliar as principais características do procedimento proposto, foi apresentado um exemplo de aplicação que aborda a integração das funcionalidades de um sistema de telefonia distribuído e um sistema de vigilância predial. A abordagem de modelagem possibilitou a identificação das funcionalidades dos dispositivos inteligentes que integram o sistema de controle em diferentes níveis de abstração e as interações que ocorrem durante o seu funcionamento. A realização deste trabalho contribui para o aprimoramento de novas abordagens para o desenvolvimento de sistemas de controle com arquiteturas heterárquicas. Estes sistemas são constituídos por dispositivos inteligentes colaborativos, que possuem um elevado grau de autonomia. / Technological advances in recent decades have motivated the development of intelligent buildings, aimed at creating environments more productive for the occupants, economically advantageous for the owners and environmentally correct. New ways of interaction between users and the buildings systems are emerging from these kinds of systems, which are not adequately treated by conventional modeling techniques. In this sense, it is necessary the study of new approaches which address these new functionalities. Thus, this work presents a proposal for a systematic approach to model and simulate the control system of the intelligent buildings. The control system is considered to be a discrete event system, where the communication between the devices that integrate it is oriented by means of asynchronous messages exchange. This approach uses the colored Petri nets in order to specify the functionalities of the building system and their devices interactions. The approach provides a structured procedure to develop models that facilitate the algorithm specification of the control system. In order to verify the main characteristics of the proposed procedure, it is presented an example that is a control system that integrates a distributed telephony system and a surveillance building system. The approach proposed enabled the identification of the main functionalities and interactions of the intelligent devices constituting the control system. The achievement of this thesis contributes to the development of new approaches to develop heterarchical control system architectures. This kind of system architectures is constituted by collaborative intelligent devices that have a high degree of autonomy.

Modern applications are required to handle and communicate an increasing amount of data. Meanwhile, distributed systems containing multiple computationally weak components becomes more common, resulting in a problematic situation. Choosing among communication strategies, used for delivering message between entities, therefore becomes crucial in order to efficiently utilize available resources. Systems where identical data is delivered to many recipients are common nowadays, but may apply an underlying communication strategy based on direct interaction between sender and receiver which is insufficient. Multicasting refers to a technique for group communication where messages can be distributed to participating nodes in a single transmission. This technique is developed to circumvent the problem of high workload on sender side and redundant traffic in the network, and constitutes the focus for this thesis. Within the area of Electronic Warfare and self-protection systems, time constitutes a critical aspect in order to provide relevant information for decision making. Self-protection systems developed by Saab, used in military aircrafts, must provide situational awareness to guarantee that correct decisions can be made at the right time. With more advanced systems, where the amount of data needed to be transmitted increases, the need of fast communication is essential to achieve quality of service. This thesis investigates how the deployment of multicast, in a distributed data-intensive system, could prepare a system for increased data exchange. The result is a communication design which allows for the system to distribute messages to a group of receivers with less effort from the sender and with reduced redundant traffic transferred over the same link. Comparative measurements are conducted between the new implementation and the old system. The result of the evaluation shows that the multicast solution both can decrease the time for message handling as well as the workload on endpoints significantly. / Nutidens applikationer måste kunna hantera och kommunicera en ökad datamängd. Samtidigt har distribuerade system bestående av många beräkningsmässigt svaga enheter blivit allt mer vanligt, vilket är problematiskt. Valet av kommunikationsstrategi, för att leverera data mellan enheter i ett system, är därför av stor betydelse för att uppnå effektivt utnyttjande av tillgängliga resurser. System där identisk information ska distribueras till flertalet mottagare är vanligt förekommande idag. Den underliggande kommunikationsstrategin som används kan dock baseras på direkt interaktion mellan sändare och mottagare vilket är ineffektivt. Multicast (Flersändning) syftar till ett samlingsbegrepp inom datorkommunikation baserat på gruppsändning av information. Denna teknik är utvecklad för att kringgå problematiken med hög belastning på sändarsidan och dessutom minska belastningen på nätverket, och utgör fokus för detta arbete. Inom telekrigföring och självskyddssystem utgör tiden en betydande faktor för att kunna tillhandahålla relevant information som kan stödja beslutsfattning. För självskyddssystem utvecklade av Saab, vilka används i militärflygplan, är situationsmedvetenhet av stor betydelse då det möjliggör för att korrekta beslut kan tas vid rätt tidpunkt. Genom utvecklingen av mer avancerade system, där mängden meddelanden som måste passera genom nätverket ökar, tillkommer höga krav på snabb kommunikation för att kunna åstadkomma kvalité. Denna uppsatsrapport undersöker hur införandet av multicast, i ett dataintensivt distribuerat system, kan förbereda ett system för ökat datautbyte. Arbetet har resulterat i en kommunikationsdesign som gör det möjligt för systemet att distribuera meddelanden till grupp av mottagare med minskad belastning på sändarsidan och mindre redundant trafik på de utgående länkarna. Jämförandet mätningar har gjorts mellan den nya implementationen och det gamla systemet. Resultaten visar att multicast-lösningen både kan reducera tiden för meddelande hantering samt belastningen på ändnoder avsevärt.