In this thesis a number of models for recommender systems are explored, all using collaborative filtering to produce their recommendations. Extra focus is put on two models: Matrix Factorization, which is a linear model and Multi-Layer Perceptron, which is a non-linear model. With an additional purpose of training the models without collecting any sensitive data from the users, both models were implemented with a learning technique that does not require the server's knowledge of the users' data, called federated learning. The federated version of Matrix Factorization is already well-researched, and has proven not to protect the users' data at all; the data is derivable from the information that the users communicate to the server that is necessary for the learning of the model. However, on the federated Multi-Layer Perceptron model, no research could be found. In this thesis, such a model is therefore designed and presented. Arguments are put forth in support of the privacy preservability of the model, along with a proof of the user data not being analytically derivable for the central server.    In addition, new ways to further put the protection of the users' data on the test are discussed. All models are evaluated on two different data sets. The first data set contains data on ratings of movies and is called MovieLens 1M. The second is a data set that consists of anonymized fund transactions, provided by the Swedish bank SEB for this thesis. Test results suggest that the federated versions of the models can achieve similar recommendation performance as their non-federated counterparts.

<p dir="ltr">A recent emphasis of distributed learning research has been on federated learning (FL), in which model training is conducted by the data-collecting devices. In traditional FL algorithms, trained models at the edge are periodically sent to a central server for aggregation, utilizing a star topology as the underlying communication graph. However, assuming access to a central coordinator is not always practical, e.g., in ad hoc wireless network settings, motivating efforts to fully decentralize FL. Consequently, Decentralized federated learning (DFL) captures FL settings where both (i) model updates and (ii) model aggregations are exclusively carried out by the clients without a central server. Inherent challenges due to distributed nature of FL training, i.e., data heterogeneity and resource heterogeneity, become even more prevalent in DFL since it lacks a central server as a coordinator. In this thesis, we present two algorithms for resource-aware DFL, which result in achieving an overall desired performance across the clients in shorter amount of time compared to existing conventional DFL algorithms which do not factor in the resource availability of clients in their approaches.</p><p dir="ltr"><br></p><p dir="ltr">In the first project, we propose EF-HC, a novel methodology for distributed model aggregations via asynchronous, event-triggered consensus iterations over the network graph topology. We consider personalized/heterogeneous communication event thresholds at each device that weigh the change in local model parameters against the available local resources in deciding whether an aggregation would be beneficial enough to incur a communication delay on the system. In the second project, we propose Decentralized Sporadic Federated Learning (DSpodFL), a DFL methodology built on a generalized notion of sporadicity in both local gradient and aggregation processes. DSpodFL subsumes many existing decentralized optimization methods under a unified algorithmic framework by modeling the per-iteration (i) occurrence of gradient descent at each client and (ii) exchange of models between client pairs as arbitrary indicator random variables, thus capturing heterogeneous and time-varying computation/communication scenarios. We analytically characterize the convergence behavior of both algorithms for strongly convex models using both a constant and a diminishing learning rate, under mild assumptions on the communication graph connectivity, data heterogeneity across clients, and gradient noises. In DSpodFL, we do the same for non-convex models as well. Our numerical experiments demonstrate that both EF-HC and DSpodFL consistently achieve improved training speeds compared with baselines under various system settings.</p>

CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / Esta dissertaÃÃo apresenta uma proposta de middleware de comunicaÃÃo baseado em Enterprise Service Bus (ESB) para sistemas federados, isto Ã, formados por sistemas de diferentes organizaÃÃes. Este trabalho nÃo aborda o problema clÃssico de sistemas federados, cujo enfoque principal à autenticaÃÃo e a seguranÃa, mas sim uma necessidade crescente de intercomunicaÃÃo de serviÃos heterogÃneos. O middleware proposto, chamado de Federated Service Bus (FSB), faz uso de ESBs internos para permitir o isolamento, aplicaÃÃo de polÃticas e roteamento de cada domÃnio que compÃe o sistema federado, visando separar interesses e evitar conflitos. Nossa proposta à modelada por redes de Petri coloridas, o que lhe atribui confiabilidade de simulaÃÃo e de validaÃÃo com base em um modelo formal matemÃtico. Assim, ganhos significativos foram obtidos na implementaÃÃo com o uso de web services e BPEL (Business Process Execution Language). A modelagem com redes de Petri coloridas nÃo sà validou o fluxo, como o documentou em detalhes e possibilitou a diminuiÃÃo no nÃmero de erros. Por fim, enquadramos o FSB em arquiteturas consolidadas com SOA (Service Oriented Achitecture), EDA (Event-Driven Architecture) e NGOSS (Next Generation Operation System and Software). / This work presents the Federated Service Bus (FSB), a communication middleware based on Enterprise Service Bus (ESB) for federated systems. We do not address the classic problem of federated systems, focused mainly on authentication and security, but a growing need for heterogeneous service intercommunication. The proposed middleware makes use of internal ESBs to allow the isolation, application of policies and routing of each domain that comprises the federal system, seeking separate interests and avoid conflicts. Our proposal is modeled using coloured Petri nets, which gives it reliability of simulation and validation based on a formal mathematical model. Thus, significant gains were achieved in the implementation with the use of web services and BPEL (Business Process Execution Language). The modeling with coloured Petri nets not only validated the flow as allowed a error reduction. Finally, the FSB is embedded with SOA (Service Oriented Achitecture), EDA (Event-Driven Architecture) and NGOSS (Next Generation Operation System and Software).

Submitted by Maria Aparecida (cidazen@gmail.com) on 2017-08-04T14:25:51Z No. of bitstreams: 1 Luiz Aurélio Batista Neto.pdf: 2595761 bytes, checksum: 07f714d6c1f7297c78081b105edc8633 (MD5) / Made available in DSpace on 2017-08-04T14:25:51Z (GMT). No. of bitstreams: 1 Luiz Aurélio Batista Neto.pdf: 2595761 bytes, checksum: 07f714d6c1f7297c78081b105edc8633 (MD5) Previous issue date: 2014-10-19 / CAPES / Cloud computing applications are vulnerable to security threats originating from the Internet, because of the resources with other users and managed by third parties sharing. The diversity of services and technologies still presents a challenge to identity integration and user data in the distributed context. To address these issues, identity management techniques, especially those using a federated approach, appear crucial to protect the information from unauthorized access and allow the exchange of resources between the different trusted parties among themselves. The objective of this work is to develop a model that allows integration between identity providers through the Security Assertion Markup Language (SAML) protocol, in order to provide access to applications in multiple domains of Cloud Computing. In this scenario, each domain users and groups services as the mechanism of representation of the user according to the identity management system used (Shibboleth or SimpleSAMLphp). The proposed model is implemented to verify its applicability. In the experiments by computer simulation, the results obtained demonstrate the feasibility of the presented model. / Aplicações de Computação em Nuvem estão vulneráveis a ameaças de segurança oriundas da Internet, por conta do compartilhamento de recursos com outros usuários e gerenciados por terceiros. A diversidade de serviços e tecnologias se apresenta ainda como desafio para integração de identidades e dados de usuários no contexto distribuído. Para lidar com essas questões, técnicas de gerenciamento de identidades, especialmente as que utilizam a abordagem federada, se mostram fundamentais para proteger as informações de acessos não autorizados e permitir o intercâmbio de recursos entre as diferentes partes confiáveis entre si. O objetivo deste trabalho é desenvolver um modelo que permita a integração entre provedores de identidades por meio do protocolo Security Assertion Markup Language (SAML), com a finalidade de prover o acesso a aplicações em múltiplos domínios de Computação em Nuvem. Neste cenário, cada domínio agrupa usuários e serviços conforme o mecanismo de representação do usuário de acordo com o sistema de gerenciamento de identidades utilizado (Shibboleth ou SimpleSAMLphp). O modelo proposto é implementado para verificar a sua aplicabilidade. Nos experimentos realizados por simulação computacional, os resultados obtidos demonstram a viabilidade do modelo apresentado.

Retailers in rural Saskatchewan are having to contend with two predominant trendsrural and retail restructuring. Decreasing rural populations, increased consumer mobility, and the chronic instability of primary industries such as agriculture and forestry continue to impact rural communities in the province. The growing presence of multinational corporations, the drive for economies of scale, and the centralization of services into larger urban centers are all influencing the retail sector, particularly in rural areas. In response to these trends, retail co-operatives operating in Northern and Central Saskatchewan have joined a larger urban-based co-op in Prince Albert to form a regional co-operative. Co-operative theory suggests this regional structure may create internal obstacles for co-ops that differ from those of private firms, as co-operatives must consider the implications of reorganization on membership structures and member relations. While most of the empirical investigation has focused on large agricultural co-operatives, less attention has been afforded to consumer co-operatives.<p>Through interviews with the delegates and managers of the Prince Albert Co-operative Association (PACA), this study examines how a multi-branch consumer co-operative has adapted to the present rural and retail milieu. It investigates the new relationships that have emerged among the key stakeholders including members, delegates, and managers as well as the new relations between the major structures, namely the branches and the central body. The research is a starting point for understanding how member and enterprise interests are mediated, communicated, and coordinated within a regional co-operative. Delegates are the focal point of the study as they play an integral role in all of these relations. The findings of the study suggest that while new relationships do form within a multi-branch system, the primary relationship between members and their local co-op branch remains relatively unaffected. Further, the study on the PACA adds to Fairtloughs (2005) work on business structural forms called triarchies. It is argued that the integration of hierarchies, heterachies and responsible autonomy in the form of a federated network reinforces the staying power of the co-op in smaller communities.

Computing infrastructures offer remote access to computing power that can be employed, e.g., to solve complex mathematical problems or to host computational services that need to be online and accessible at all times. From the perspective of the infrastructure provider, large amounts of distributed and often heterogeneous computer resources need to be united into a coherent platform that is then made accessible to and usable by potential users. Grid computing and cloud computing are two paradigms that can be used to form such unified computational infrastructures. Resources from several independent infrastructure providers can be joined to form large-scale decentralized infrastructures. The primary advantage of doing this is that it increases the scale of the available resources, making it possible to address more complex problems or to run a greater number of services on the infrastructures. In addition, there are advantages in terms of factors such as fault-tolerance and geographical dispersion. Such multi-domain infrastructures require sophisticated management processes to mitigate the complications of executing computations and services across resources from different administrative domains. This thesis contributes to the development of management processes for distributed infrastructures that are designed to support multi-domain environments. It describes investigations into how fundamental management processes such as scheduling and accounting are affected by the barriers imposed by multi-domain deployments, which include technical heterogeneity, decentralized and (domain-wise) self-centric decision making, and a lack of information on the state and availability of remote resources. Four enabling technologies or approaches are explored and developed within this work: (I) The use of explicit definitions of cloud service structure as inputs for placement and management processes to ensure that the resulting placements respect the internal relationships between different service components and any relevant constraints. (II) Technology for the runtime adaptation of Virtual Machines to enable the automatic adaptation of cloud service contexts in response to changes in their environment caused by, e.g., service migration across domains. (III) Systems for managing meta-data relating to resource usage in multi-domain grid computing and cloud computing infrastructures. (IV) A global fairshare prioritization mechanism that enables computational jobs to be consistently prioritized across a federation of several decentralized grid installations. Each of these technologies will facilitate the emergence of decentralized computational infrastructures capable of utilizing resources from diverse infrastructure providers in an automatic and seamless manner. / <p>Note that the author changed surname from Henriksson to Espling in 2011</p>

Retailers in rural Saskatchewan are having to contend with two predominant trendsrural and retail restructuring. Decreasing rural populations, increased consumer mobility, and the chronic instability of primary industries such as agriculture and forestry continue to impact rural communities in the province. The growing presence of multinational corporations, the drive for economies of scale, and the centralization of services into larger urban centers are all influencing the retail sector, particularly in rural areas. In response to these trends, retail co-operatives operating in Northern and Central Saskatchewan have joined a larger urban-based co-op in Prince Albert to form a regional co-operative. Co-operative theory suggests this regional structure may create internal obstacles for co-ops that differ from those of private firms, as co-operatives must consider the implications of reorganization on membership structures and member relations. While most of the empirical investigation has focused on large agricultural co-operatives, less attention has been afforded to consumer co-operatives.<p>Through interviews with the delegates and managers of the Prince Albert Co-operative Association (PACA), this study examines how a multi-branch consumer co-operative has adapted to the present rural and retail milieu. It investigates the new relationships that have emerged among the key stakeholders including members, delegates, and managers as well as the new relations between the major structures, namely the branches and the central body. The research is a starting point for understanding how member and enterprise interests are mediated, communicated, and coordinated within a regional co-operative. Delegates are the focal point of the study as they play an integral role in all of these relations. The findings of the study suggest that while new relationships do form within a multi-branch system, the primary relationship between members and their local co-op branch remains relatively unaffected. Further, the study on the PACA adds to Fairtloughs (2005) work on business structural forms called triarchies. It is argued that the integration of hierarchies, heterachies and responsible autonomy in the form of a federated network reinforces the staying power of the co-op in smaller communities.

This research develops a computer simulation method for federating an Arena© port operations model and a VISSIM© roadway network operations model. The development of this method is inspired by the High Level Architecture (HLA) standard for federating simulations, and incorporates several elements of the HLA principles into its design. The federated simulation model is then tested using a time-lag experiment to demonstrate the presence of feedback loops between federated model components wherein changes to input parameters of one model during runtime can be shown to affect the operational performance of the other model. This experiment also demonstrates how several initial transient phase and steady state operating characteristics of the federated system can be determined from the federation output data. The results indicate that the method developed in this study is capable of capturing the dynamic interaction of two models in federated simulation. It is shown that feedback loops can exist between two models in federated simulation. Most notably, the federation output shows that increased traffic volume in the roadway network model influences the accumulation of containers in the port terminal queue of the port model. The federation output also shows that increased container volume leaving the port terminal model affects both port and road truck utilization, as well as the total number of port trucks in the roadway network model. Challenges and future directions for research in federating transportation-related simulations are also presented.

Zur Erledigung einer Aufgabe kann der Benutzer mit verschiedenen Endgeräten interagieren, welche unterschiedliche Interaktionsarten (Modalitäten) anbieten. Dabei gibt es jedoch kein Endgerät, welches alle erdenkbaren Modalitäten unterstützt. Aus diesem Grund wird eine komponentenbasierte Integrationsschicht auf Basis einer Komponentenplattform entwickelt, die dem Nutzer die gewünschte Freiheit bei der Wahl der Endgeräte und somit der Modalitäten ermöglicht. Als Ausgangsbasis dafür dient das W3C Multimodal Interaction Framework. Mit Hilfe der Integrationsschicht kann der Nutzer beispielsweise Endgeräteföderationen erzeugen, die einzeln oder gemeinsam zur Interaktion verwendet werden können. Die Integrationsschicht besitzt verschiedene Konzepte, um z.B. Geschäftslogik zur Laufzeit zu verteilen, Komponentenausfälle zu behandeln und die auf verschiedene Endgeräte verteilte Nutzerschnittstelle zu synchronisieren. Die entwickelten Konzepte wurden prototypisch implementiert, validiert und auf Performanz untersucht.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2004. / Includes bibliographical references. / Also available by subscription via World Wide Web / xv, 252 leaves, bound ill., map 29 cm