Recommender systems are an advanced form of software applications, more specifically decision-support systems, that efficiently assist the users in finding items of their interest. Recommender systems have been applied to many domains from music to e-commerce, movies to software services delivery and tourism to news by exploiting available information to predict and provide recommendations to end user. The suggestions generated by recommender systems tend to narrow down the list of items which a user may overlook due to the huge variety of similar items or users’ lack of experience in the particular domain of interest. While the performance of traditional recommender systems, which rely on relatively simpler information such as content and users’ filters, is widely accepted, their predictive capability perfomrs poorly when local context of the user and situated actions have significant role in the final decision. Therefore, acceptance and incorporation of context of the user as a significant feature and development of recommender systems utilising the premise becomes an active area of research requiring further investigation of the underlying algorithms and methodology. This thesis focuses on categorisation of contextual and non-contextual features within the domain of context-aware recommender system and their respective evaluation. Further, application of the Multilayer Perceptron Model (MLP) for generating predictions and ratings from the contextual and non-contextual features for contextual recommendations is presented with support from relevant literature and empirical evaluation. An evaluation of specifically employing artificial neural networks (ANNs) in the proposed methodology is also presented. The work emphasizes on both algorithms and methodology with three points of consideration: contextual features and ratings of particular items/movies are exploited in several representations to improve the accuracy of recommendation process using artificial neural networks (ANNs), context features are combined with user-features to further improve the accuracy of a context-aware recommender system and lastly, a combination of the item/movie features are investigated within the recommendation process. The proposed approach is evaluated on the LDOS-CoMoDa dataset and the results are compared with state-of-the-art approaches from relevant published literature.

A Computação Ciente de Contexto permite a obtenção e utilização de informações de contexto adquiridas de dispositivos computacionais no ambiente, com o objetivo de prover serviços; esta dinâmica aliada à evolução das redes de computadores vem provocando profundas modificações nos aspectos sociais e comportamentais das pessoas, uma vez que gradativamente têm necessidade de viverem imersas na tecnologia e integradas ao ambiente, com transparência e mobilidade, e de tal forma que as aplicações de software se adaptam ao comportamento das pessoas e nas informações de contexto capturadas do ambiente. Um dos desafios desta interação ser humano - ambiente - tecnologia - ubiqüidade é garantir a segurança. Como principal inovação e contribuição, esta tese propõe um mecanismo de autenticação contínua de usuários que faz uso de informações de contexto do ambiente, da análise do comportamento do usuário, da biometria facial, das teorias comportamentais de Skinner e da Confiança Matemática da Teoria das Evidências de Dempster-Shafer, para compor uma política de segurança adaptativa e um Sistema de Autenticação Contínua de Usuários Conhecidos - KUCAS (Known User Continuous Authentication System), que estabelece níveis de confiança para autenticar o usuário através da análise do comportamento dele em um ambiente ou domínio específico nas redes de computadores, num determinado período de tempo. A dinâmica de gerenciamento incluso nesse sistema compara o comportamento atual com o histórico de comportamentos anteriores do usuário e com as restrições de atribuição de confiança; caso haja indícios de mudanças no comportamento do usuário, aciona por meio de sensores, a Tecnologia de Reconhecimento Facial Tridimensional (3D), que captura a imagem da face do usuário, validando-a e armazenando-a nos bancos de dados de imagens; havendo incertezas e divergências, mecanismos de segurança e sinais de alerta são acionados. O Sistema KUCAS proposto possui uma infra-estrutura de um framework F-KUCAS, um Módulo de Segurança S-KUCAS e um Algoritmo de Autenticação A-KUCAS. / Context-aware Computing allows to obtain and use context informations acquired through devices in the environment, with the goal to provide services. This dynamics, allied to the computer networks evolution, has been provoking deep modifications in peoples social and behavior aspects, seeing that they have the necessity to live immersed in technology and integrated with the environment, with transparency and mobility, anywhere, anytime, so that the software applications adapt themselves to the persons behavior, based on the context information captured through the environment. One of the challenges of this human ? environment - technology ? ubiquity interaction is to provide security. As main innovation and contribution, this thesis presents an authentication mechanism of users which makes use of environmental context information, users behavior analysis, the face recognition technology, the behavior theories of Skinner and the Mathematical Confidence of the Theory of the Evidences of Dempster-Shafer, to compose an adaptative security policy and the Known User Continuous Authentication System (KUCAS) that establishes trust levels to authenticate the user by his behavior analysis in a specific domain of the computer networks, in a period of time. The dynamics of enclosed management in this system compares the current behavior with the users previous behaviors description and with the trust restrictions. In case of indications of changes in the users behavior, the 3D Technology Face Recognition is set in motion by sensors, which capture the image of the users face, validating it and storing it in the data bases of images. If there are uncertainties and divergences, mechanisms of security and signals of alert are set in motion. The KUCAS System has an infrastructure of one framework F-KUCAS, a Security Module S-KUCAS and an Algorithm of Authentication A-KUCAS.

Submitted by Maria Aparecida (cidazen@gmail.com) on 2017-07-26T13:52:12Z No. of bitstreams: 1 Debora Stefanello.pdf: 4211863 bytes, checksum: 01fdbcf038800472fbd854b22bc2e341 (MD5) / Made available in DSpace on 2017-07-26T13:52:12Z (GMT). No. of bitstreams: 1 Debora Stefanello.pdf: 4211863 bytes, checksum: 01fdbcf038800472fbd854b22bc2e341 (MD5) Previous issue date: 2017-01-25 / CAPES / In recent years, some research has taken into account problems related to the development of software systems, especially those that make use of context, i.e. context-aware systems. In this dissertation the complexity of context-aware system development is discussed. The proposed solution aims to provide support for the context-aware system development through a framework based on MDE and Weaving. On the one hand, MDE allows the use of models to manage complexity in software development, while the weaving technique supports the creation of interrelations between elements of different but complementary models. The weaving technique is used to create a weaving model that establishes interrelationships between the elements of a Platform Independent Model (PIM) and several Platform Description Model (PDMs). An implementation of the proposed framework and an illustrative example help to understand the proposal and its feasibility. A comparison between the proposed solution and the works found in the literature Done, showing the negative and positive points of the proposed solution. / Nos últimos anos, algumas pesquisas têm levado em conta as problemáticas relacionadas ao desenvolvimento de sistema de software, em especial, aqueles que fazem o uso de contexto, i.e. context-aware systems. Nesta dissertação de mestrado, abordase a complexidade no desenvolvimento de context-aware system. A solução proposta visa fornecer suporte para o desenvolvimento de context-aware system através de um framework baseado em MDE e Weaving. Por um lado, MDE permite a utilização de modelos para gerenciar a complexidade no desenvolvimento de sofware, enquanto a técnica de weaving suporta a criação de inter-relacionamentos entre elementos de modelos diferentes, mas complementares. A técnica de weaving é utilizada para criar um modelo de weaving que estabelece inter-relacionamentos entre os elementos de um PIM (Platform Independent Model) e de vários PDMs (Platform Description Model). Uma implementação do framework proposto e um exemplo ilustrativo ajudam a entender a proposta e mostram a sua viabilidade. Um comparativo entre a solução proposta e os trabalhos encontrados na literatura é feito, mostrando os pontos negativos e positivos da solução proposta.

Submitted by Maria Aparecida (cidazen@gmail.com) on 2017-08-31T13:25:42Z No. of bitstreams: 1 Claudio Manoel.pdf: 2235875 bytes, checksum: 09f2ae854210974f87252bad3c5b1df9 (MD5) / Made available in DSpace on 2017-08-31T13:27:28Z (GMT). No. of bitstreams: 1 Claudio Manoel.pdf: 2235875 bytes, checksum: 09f2ae854210974f87252bad3c5b1df9 (MD5) Previous issue date: 2015-05-27 / The use and popularity of mobile devices has been growing vertiginously, as well an the cloud computing as instrument to store data and services, making feasible the combination of these two technologies. One of the biggest obstacles is the mobile device’s security and ergonomics to provide security for transporting its data without performance degradation. This work proposes a context-aware security mechanism for mobile devices in cloud computing. In addition, it is used the TLS technology to create a secure channel of data sent between mobile device’s client and the cloud server, authenticating them via public key cryptography. At the same time, it provides an appropriate level of security, and analyses the context of the mobile device from the Fuzzy logic. The impact of the mechanism on the mobile device’s performance were measured through experiments. / O uso e a popularidade dos dispositivos móveis vem crescendo vertiginosamente, bem como a computação em nuvem como instrumento para armazenar dados e serviços, tornando-se viável a união dessas duas tecnologias. Um dos maiores obstáculos é a questão da segurança e ergonomia do dispositivo móvel que necessita provê-lo ao trafegar dados sem haver degradação de seu desempenho. Este trabalho propõe então um mecanismo de segurança ciente do contexto para Computação em Nuvem Móvel. Em adição, utiliza-se a tecnologia Transport Layer Security (TLS) para criar um canal seguro de envio de dados entre o cliente do dispositivo móvel e o servidor da Nuvem, autenticando-o por meio de criptografia de chave pública. Paralelamente, para prover um nível de segurança apropriado, analisase o contexto do dispositivo móvel a partir da lógica Fuzzy. O impacto do mecanismo no desempenho do dispositivo móvel foi medido por meio de experimentos.

O processo de digitalização da TV em diversos países do mundo tem contribuído para o aumento do volume de programas de TV, o que gera uma sobrecarga de informação. Consequentemente, o usuário está enfrentando dificuldade para encontrar os programas de TV favoritos dentre as várias opções disponíveis. Diante deste cenário, os sistemas de recomendação destacam-se como uma possível solução. Tais sistemas são capazes de filtrar itens relevantes de acordo com as preferências do usuário ou de um grupo de usuários que possuem perfis similares. Entretanto, em diversas recomendações o interesse do usuário pode depender do seu contexto. Assim, torna-se importante estender as abordagens tradicionais de recomendação personalizada por meio da exploração do contexto do usuário, o que poderá melhorar a qualidade das recomendações. Para isso, este trabalho descreve uma infraestrutura de software de suporte ao desenvolvimento e execução de sistemas de recomendação sensíveis ao contexto para TV Digital Interativa - intitulada de PersonalTVware. A solução proposta fornece componentes que implementam técnicas avançadas para recomendação de conteúdo e processamento de contexto. Com isso, os desenvolvedores de sistemas de recomendação concentram esforços na lógica de apresentação de seus sistemas, deixando questões de baixo nível para o PersonalTVware gerenciar. As modelagens de usuário, e do contexto, essenciais para o desenvolvimento do PersonalTVware, são representadas por padrões de metadados flexíveis usados na TV Digital Interativa (MPEG-7 e TV-Anytime), e suas devidas extensões. A arquitetura do PersonalTVware é composta por dois subsistemas: dispositivo do usuário e provedor de serviços. A tarefa de predição de preferências contextuais é baseada em métodos de aprendizagem de máquina, e a filtragem de informação sensível ao contexto tem como base a técnica de filtragem baseada em conteúdo. O conceito de perfil contextual também é apresentado e discutido. Para demonstrar e validar as funcionalidades do PersonalTVware em um cenário de uso, foi desenvolvido um sistema de recomendação sensível ao contexto como estudo de caso. / The process of digitalization of TV in several countries around the world has, contributed to increase the volume of TV programs offered and it leads, to information overload problem. Consequently, the user facing the difficulty to find their favorite TV programs in view of various available options. Within this scenario, the recommender systems stand out as a possible solution. These systems are capable of filtering relevant items according to the user preferences or the group of users who have similar profiles. However, the most of the recommender systems for Interactive Digital TV has rarely take into consideration the users contextual information in carrying out the recommendation. However, in many recommendations the user interest may depend on the context. Thus, it becomes important to extend the traditional approaches to personalized recommendation of TV programs by exploiting the context of user, which may improve the quality of the recommendations. Therefore, this work presents a software infrastructure in an Interactive Digital TV environment to support context-aware personalized recommendation of TV programs entitled PersonalTVware. The proposed solution provides components which implement advanced techniques to recommendation of content and context management. Thus, developers of recommender systems can concentrate efforts on the presentation logic of their systems, leaving low-level questions for the PersonalTVware managing. The modeling of user and context, essential for the development of PersonalTVware, are represented by granular metadata standards used in the Interactive Digital TV field (MPEG-7 and TV-Anytime), and its extensions required. The PersonalTVware architecture is composed by two subsystems: the users device and the service provider. The task of inferring contextual preferences is based on machine learning methods, and context-aware information filtering is based on content-based filtering technique. The concept of contextual user profile is presented and discussed. To demonstrate the functionalities in a usage scenario a context-aware recommender system was developed as a case study applying the PersonalTVware.

A certificate based approach is proposed for access control operations of context aware systems for multi domain environments. New model deals with the removal of inter-domain communication requirement in access request evaluation process. The study is applied on a prototype implementation with configuration for two dierent cases to show the applicability of the proposed certificate based, context aware access control model for multi domain environments. The outputs for the cases show that proposed access control model can satisfy the requirements of a context aware access control model while removing inter domain communication needs which may cause some latency in access request evaluation phase.

Potentially transformational ideas in several applications of human and computer interaction form the motivation for this work. It is targeted towards a systematic approach to the design of systems with complex, intelligent and interactive exchange of information between a system and the environment it is meant to monitor, and gather knowledge about. The Pahl and Beitz systematic design method is modified with the inclusion of generic sub-systems from Living Systems Theory, modeling and simulation tools and other adaptations within the context of the validation square to synthesize a design method for the design of systems with intelligent and interactive information flow. The validation of the proposed design method is carried out with the aid of an example wherein a motion capture system is designed based on the Nintendo Wii Remote(TM). Results include an evaluation of the performance of a prototype as well as the design method itself in the context of the requirements that the method must fulfill.

隨著無線網路環境的普及，越來越多行動工作者可以透過隨身的手持設備進行網路漫遊，即時地存取不同的服務。另外亦可以經由公司的虛擬專有網路來存取企業內部資料、電子郵件及其它應用程式。不論是針對企業或是網路服務業者而言，為了要能夠確保網路環境上的安全性，眾多的行動工作者在進行漫遊時，身分必須被驗證，進而才能被授予各項服務的存取權。此外，還必需根據使用者服務使用的情況進行計費，來提升服務提供者的收益。 因此在無線區域網路中，結合一套認證、授權、計費的架構(Authentication, Authorization, Accounting Architecture, AAA Architecture)，使得網路服務業者能夠有效地來管理龐大行動工作者的跨網路漫遊服務。 本研究提出一個以情境知覺運算(context-aware computing)為基礎的AAA架構。以情境來設計資源存取政策，因此系統偵測到行動工作者情境上的改變，根據已定義好的存取政策，動態地進行身分驗證及調整授權服務，最後再依不同的服務使用等級、連線時間與網路使用量等來計費。本論文以漫遊服務與企業虛擬專有網路為例，說明在此架構下如何針對不同的情境進行身分認證、與服務授權。 / With the popularity of the Wireless LAN, mobile workers are able to access various services or resources with seamless roaming, as well as mobile VPN, just via their handheld devices. Not only for the corporations but the Internet Service Providers(ISP), a secure and trusted remote access is required. User identity should be authenticated in advance, and the service providers grant or deny mobile users the access to resources according to their statuses. Besides, a usage-based accounting and billing is crucial to provide commercialized services within WLAN, and to benefit those service providers. As a result, a AAA architecture designed for coordinating the authentication, authorization and accounting between different administrative networks is required with urgent need. The objective of this research is to provide a context-aware based AAA architecture which adopts context as the design principle to define access control policies. So the system can detect the changing contexts of mobile workers, re-authenticate user identity, adjust dynamically service permissions in the light of context-based access control policies, and bill the user taking into account the contexts efficiently. In this research, we take examples of roaming services and VPN to describe how the architecture works.

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Rusell M. Mersereau; Committee Member: Biing Hwang (Fred) Juang; Committee Member: Christopher E. Heil; Committee Member: Georgia Vachtsevanos; Committee Member: James H. McClellan. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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