Recommender Systems and their Security Concerns

Instead of simply using two-dimensional User × Item features, advanced recommender systems rely on more additional dimensions (e.g. time, location, social network) in order to provide better recommendation services. In the first part of this paper, we will survey a variety of dimension features and show how they are integrated into the recommendation process. When the service providers collect more and more personal information, it brings great privacy concerns to the public. On another side, the service providers could also suffer from attacks launched by malicious users who want to bias the recommendations. In the second part of this paper, we will survey attacks from and against recommender service providers, and existing solutions

Context-Aware Recommendation Systems in Mobile Environments

Nowadays, the huge amount of information available may easily overwhelm users when they need to take a decision that involves choosing among several options. As a solution to this problem, Recommendation Systems (RS) have emerged to offer relevant items to users. The main goal of these systems is to recommend certain items based on user preferences. Unfortunately, traditional recommendation systems do not consider the user’s context as an important dimension to ensure high-quality recommendations. Motivated by the need to incorporate contextual information during the recommendation process, Context-Aware Recommendation Systems (CARS) have emerged. However, these recent recommendation systems are not designed with mobile users in mind, where the context and the movements of the users and items may be important factors to consider when deciding which items should be recommended. Therefore, context-aware recommendation models should be able to effectively and efficiently exploit the dynamic context of the mobile user in order to offer her/him suitable recommendations and keep them up-to-date.The research area of this thesis belongs to the fields of context-aware recommendation systems and mobile computing. We focus on the following scientific problem: how could we facilitate the development of context-aware recommendation systems in mobile environments to provide users with relevant recommendations? This work is motivated by the lack of generic and flexible context-aware recommendation frameworks that consider aspects related to mobile users and mobile computing. In order to solve the identified problem, we pursue the following general goal: the design and implementation of a context-aware recommendation framework for mobile computing environments that facilitates the development of context-aware recommendation applications for mobile users. In the thesis, we contribute to bridge the gap not only between recommendation systems and context-aware computing, but also between CARS and mobile computing.<br /

Evaluating collaborative filtering over time

Recommender systems have become essential tools for users to navigate the plethora of content in the online world. Collaborative filtering—a broad term referring to the use of a variety, or combination, of machine learning algorithms operating on user ratings—lies at the heart of recommender systems’ success. These algorithms have been traditionally studied from the point of view of how well they can predict users’ ratings and how precisely they rank content; state of the art approaches are continuously improved in these respects. However, a rift has grown between how filtering algorithms are investigated and how they will operate when deployed in real systems. Deployed systems will continuously be queried for personalised recommendations; in practice, this implies that system administrators will iteratively retrain their algorithms in order to include the latest ratings. Collaborative filtering research does not take this into account: algorithms are improved and compared to each other from a static viewpoint, while they will be ultimately deployed in a dynamic setting. Given this scenario, two new problems emerge: current filtering algorithms are neither (a) designed nor (b) evaluated as algorithms that must account for time. This thesis addresses the divergence between research and practice by examining how collaborative filtering algorithms behave over time. Our contributions include: 1. A fine grained analysis of temporal changes in rating data and user/item similarity graphs that clearly demonstrates how recommender system data is dynamic and constantly changing. 2. A novel methodology and time-based metrics for evaluating collaborative filtering over time, both in terms of accuracy and the diversity of top-N recommendations. 3. A set of hybrid algorithms that improve collaborative filtering in a range of different scenarios. These include temporal-switching algorithms that aim to promote either accuracy or diversity; parameter update methods to improve temporal accuracy; and re-ranking a subset of users’ recommendations in order to increase diversity. 4. A set of temporal monitors that secure collaborative filtering from a wide range of different temporal attacks by flagging anomalous rating patterns. We have implemented and extensively evaluated the above using large-scale sets of user ratings; we further discuss how this novel methodology provides insight into dimensions of recommender systems that were previously unexplored. We conclude that investigating collaborative filtering from a temporal perspective is not only more suitable to the context in which recommender systems are deployed, but also opens a number of future research opportunities

Social software for music

Tese de mestrado integrado. Engenharia Informática e Computação. Faculdade de Engenharia. Universidade do Porto. 200

Privacy on the Web: Analysing Online Advertising Networks

Το θέμα της διπλωματικής αφορά ζητήματα ιδιωτικότητας στο Διαδίκτυο, με έμφαση την ιχνηλάτηση χρηστών για το σκοπό στοχευμένων διαφημίσεων. Θα μελετηθούν οι τεχνολογίες που χρησιμοποιούνται σε αυτήν την κατεύθυνση, και θα αξιολογηθεί η τρέχουσα κατάσταση υπό το πρίσμα του σχετικού νομικού πλαισίου, που είναι ο Γενικός Κανονισμός Προστασίας Δεδομένων(GDPR- 2016/679) της ΕΕ, αλλά και η e-Privacy οδηγία. Πιο συγκεκριμένα αναλύονται οι προσπάθειες των διαφημιστικών δικτύων, ώστε να λαμβάνουν όσο το δυνατόν περισσότερες προσωπικές πληροφορίες από τους χρήστες, οι οποίες χρησιμοποιούνται κυρίως για εμπορικούς σκοπούς, οι οποίες ωστόσο μπορεί και να υπερβαίνουν τη στοχευμένη διαφήμιση. Υπάρχει μια εκτεταμένη ανάλυση σχετικά με την υποδομή, τις αλληλεπιδράσεις μεταξύ των στοιχείων και τις τεχνολογίες που επιτρέπουν την προβολή διαφημίσεων και την ανταλλαγή προσωπικών δεδομένων. Τέλος, αναλύονται ορισμένες πιθανές λύσεις σχετικά με την παρακολούθηση των χρηστών, έπειτα από την κατάργηση των third party data λόγω των αυστηρών μέτρων σχετικά με τη συλλογή προσωπικών δεδομένων, που εφαρμόζει η ΕΕ.This thesis mainly focuses on the big picture of the current stage of user data collection and protection and at the same time discuss scientific solutions that aim at protecting web users from numerous privacy threats which are caused by the online advertising industry. There is an extensive analysis about the infrastructure, the interactions among the elements, and the technologies enabling the delivery of ads and the use of personal data. The paper provides scientific details in order the reader to understand the present advertising ecosystem, and the privacy risks users are exposed to. There is a detailed discussion about the measures taken by European Union with a single purpose, to put in order the chaos that exists in the global system of interconnected computer networks called Internet. Except of the analysis of the GDPR, there is an investigation about the trackers that use our data while we access any domain and the results are provided precisely. Finally, there is a part, where some possible solutions of tracking users are discussed, after the fade of third party data due to the strict measures regarding users data collection, announced by the EU

Web2.0, knowledge sharing and privacy in E-learning

Quand le E-learning a émergé il ya 20 ans, cela consistait simplement en un texte affiché sur un écran d'ordinateur, comme un livre. Avec les changements et les progrès dans la technologie, le E-learning a parcouru un long chemin, maintenant offrant un matériel éducatif personnalisé, interactif et riche en contenu. Aujourd'hui, le E-learning se transforme de nouveau. En effet, avec la prolifération des systèmes d'apprentissage électronique et des outils d'édition de contenu éducatif, ainsi que les normes établies, c’est devenu plus facile de partager et de réutiliser le contenu d'apprentissage. En outre, avec le passage à des méthodes d'enseignement centrées sur l'apprenant, en plus de l'effet des techniques et technologies Web2.0, les apprenants ne sont plus seulement les récipiendaires du contenu d'apprentissage, mais peuvent jouer un rôle plus actif dans l'enrichissement de ce contenu. Par ailleurs, avec la quantité d'informations que les systèmes E-learning peuvent accumuler sur les apprenants, et l'impact que cela peut avoir sur leur vie privée, des préoccupations sont soulevées afin de protéger la vie privée des apprenants. Au meilleur de nos connaissances, il n'existe pas de solutions existantes qui prennent en charge les différents problèmes soulevés par ces changements. Dans ce travail, nous abordons ces questions en présentant Cadmus, SHAREK, et le E-learning préservant la vie privée. Plus précisément, Cadmus est une plateforme web, conforme au standard IMS QTI, offrant un cadre et des outils adéquats pour permettre à des tuteurs de créer et partager des questions de tests et des examens. Plus précisément, Cadmus fournit des modules telles que EQRS (Exam Question Recommender System) pour aider les tuteurs à localiser des questions appropriées pour leur examens, ICE (Identification of Conflits in Exams) pour aider à résoudre les conflits entre les questions contenu dans un même examen, et le Topic Tree, conçu pour aider les tuteurs à mieux organiser leurs questions d'examen et à assurer facilement la couverture des différent sujets contenus dans les examens. D'autre part, SHAREK (Sharing REsources and Knowledge) fournit un cadre pour pouvoir profiter du meilleur des deux mondes : la solidité des systèmes E-learning et la flexibilité de PLE (Personal Learning Environment) tout en permettant aux apprenants d'enrichir le contenu d'apprentissage, et les aider à localiser nouvelles ressources d'apprentissage. Plus précisément, SHAREK combine un système recommandation multicritères, ainsi que des techniques et des technologies Web2.0, tels que le RSS et le web social, pour promouvoir de nouvelles ressources d'apprentissage et aider les apprenants à localiser du contenu adapté. Finalement, afin de répondre aux divers besoins de la vie privée dans le E-learning, nous proposons un cadre avec quatre niveaux de vie privée, ainsi que quatre niveaux de traçabilité. De plus, nous présentons ACES (Anonymous Credentials for E-learning Systems), un ensemble de protocoles, basés sur des techniques cryptographiques bien établies, afin d'aider les apprenants à atteindre leur niveau de vie privée désiré.E-learning emerged over 20 years ago, and was merely book like text displayed on a computer screen. With the changes and advances in technology, E-learning has come a long way, providing personal and interactive rich content. Today, E-learning is again going through major changes. Indeed, with the proliferation of E-learning systems and content authoring tools, as well as established standards, it has become easier to share and reuse learning content. Moreover, with the shift to learner centered education and the effect of Web2.0 techniques and technologies, learners are no longer just recipients of the learning content, but can play an active role into enriching such content. Additionally, with the amount of information E-learning systems can gather about learners, and the impact this has on their privacy, concerns are being raised in order to protect learners’ privacy. Nonetheless, to the best of our knowledge, there is no existing work that supports the various challenges raised by these changes. In this work, we address these issues by presenting Cadmus, SHAREK, and privacy preserving E-learning. Specifically, Cadmus is an IMS QTI compliant web based assessment authoring tool, offering the proper framework and tools to enable tutors author and share questions and exams. In detail, Cadmus provides functionalities such as the EQRS (Exam Questions Recommender System) to help tutors locate suitable questions, ICE (Identification of Conflicts in Exams) to help resolve conflicts between questions within the same exam, and the topic tree, designed to help tutors better organize their exam questions and easily ensure the content coverage of their exams. On the other hand, SHAREK (Sharing REsources and Knowledge) provides the framework to take advantage of both the rigidity of E-learning systems and the flexibility of PLEs (Personal Learning Environment) while enabling learners to enrich the learning content, and helping them locate new learning resources. Specifically, SHAREK utilizes a multi-criteria content based recommender system, and combines Web2.0 technologies and techniques such as RSS and social web to promote new learning resources and help learners locate suitable content. Lastly, in order to address the various needs for privacy in E-learning, we propose a framework with four levels of privacy, and four levels of tracking, and we detail ACES (Anonymous Credentials for E-learning Systems), a set of protocols, based on well established cryptographic techniques, to help learners achieve their desired level of privacy

Improving accuracy of recommender systems through triadic closure

The exponential growth of social media services led to the information overload problem which information filtering and recommender systems deal by exploiting various techniques. One popular technique for making recommendations is based on trust statements between users in a social network. Yet explicit trust statements are usually very sparse leading to the need for expanding the trust networks by inferring new trust relationships. Existing methods exploit the propagation property of trust to expand the existing trust networks; however, their performance is strongly affected by the density of the trust network. Nevertheless, the utilisation of existing trust networks can model the users’ relationships, enabling the inference of new connections. The current study advances the existing methods and techniques on developing a trust-based recommender system proposing a novel method to infer trust relationships and to achieve a fully-expanded trust network. In other words, the current study proposes a novel, effective and efficient approach to deal with the information overload by expanding existing trust networks so as to increase accuracy in recommendation systems. More specifically, this study proposes a novel method to infer trust relationships, called TriadicClosure. The method is based on the homophily phenomenon of social networks and, more specifically, on the triadic closure mechanism, which is a fundamental mechanism of link formation in social networks via which communities emerge naturally, especially when the network is very sparse. Additionally, a method called JaccardCoefficient is proposed to calculate the trust weight of the inferred relationships based on the Jaccard Cofficient similarity measure. Both the proposed methods exploit structural information of the trust graph to infer and calculate the trust value. Experimental results on real-world datasets demonstrate that the TriadicClosure method outperforms the existing state-of-the-art methods by substantially improving prediction accuracy and coverage of recommendations. Moreover, the method improves the performance of the examined state-of-the-art methods in terms of accuracy and coverage when combined with them. On the other hand, the JaccardCoefficient method for calculating the weight of the inferred trust relationships did not produce stable results, with the majority showing negative impact on the performance, for both accuracy and coverage

Recent Advances in Social Data and Artificial Intelligence 2019

The importance and usefulness of subjects and topics involving social data and artificial intelligence are becoming widely recognized. This book contains invited review, expository, and original research articles dealing with, and presenting state-of-the-art accounts pf, the recent advances in the subjects of social data and artificial intelligence, and potentially their links to Cyberspace

Smart Fitness System: Training Programming

Sistemas de recomendação no geral estão a ser cada vez mais usados por empresas que procuram oferecer uma experiência de utilização mais individual e personalizada aos seus clientes. Obter feedback em transações de negócio online nunca foi tão fácil e acessível, o que apenas ajuda a catalisar a evolução dos sistemas de recomendação. Adicionalmente, o uso de dispositivos tecnológicos como smartphones e computadores, juntamente com a conexão à internet, estão também a crescer a um ritmo acelerado sem sinal de paragem em vista. Juntando-se a este grupo de indústrias em crescimento está a indústria fitness, que está a ficar cada vez mais popular. Com isto, mais e mais pessoas estão a começar a usar os dispositivos mencionados anteriormente em combinação com as suas atividades fitness, para aumentar o seu desempenho, monitorizar progresso, definir objetivos, entre outros. Consequentemente, o mercado para sistemas fitness (p.e. aplicações fitness) está a aumentar e já é bastante denso. No entanto, a qualidade associada com tais sistemas fica um pouco aquém tanto em termos de inovação como de funcionalidades essenciais. Como resultado disto, este projeto propôs uma solução – um sistema fitness sob a forma de uma aplicação móvel aliada a um poderoso sistema de recomendação. Este sistema é pretendido que providencie uma experiência mais individual e personalizada para qualquer tipo de utilizador fitness através da oferta de funcionalidades essenciais como registo e monitorização de informação, análise de progresso, e também através de funcionalidades inovadoras como a implementação de um sistema de recomendação capaz de sugerir tópicos relacionados com fitness (p.e. regimes de treino ou exercícios específicos) baseado em múltiplos fatores como os objetivos, características individuais e historial de cada utilizador. Além do mais, deve também oferecer um assistente pessoal virtual, onde os utilizadores podem expressar as suas questões e dúvidas, e tê-las respondidas instantaneamente por um chatbot. Durante o desenvolvimento foi decidido que um segundo sistema de recomendação seria necessário para melhorar o sistema no geral. Este, o sistema, depois de implementado, foi avaliado e pode ser concluído que o resultado foi um sucesso, tendo passado em todas as métricas definidas, exceto uma, com classificações médias nos questionários de satisfação acima de 4/5. O feedback obtido por um especialista no sistema de recomendação foi altamente vantajoso e no geral decentemente positivo, apenas com algumas questões que necessitam de melhoramento. Embora o sistema de recomendação inteligente não tenha conseguido ser testado com informação aplicável, a investigação e trabalho feito constituem uma mais valia caso mais tarde exista a possibilidade de aplicar dados reais.Recommender systems in general are increasingly becoming more exploited by companies who seek to provide a more individual and personalized user-experience to their customers. The fact that providing feedback on online business transactions is also becoming ever so easier only helps to catalyze the evolution of recommender systems. Moreover, the use of technological devices such as smartphones and computers, in conjunction with an internet connection, are also continuing to grow at a fast pace, with no slowing down in sight. Joining on this group of growing industries is the fitness sector, which is becoming increasingly popular. With this, more and more people are starting to use the aforementioned devices in combination with their fitness activities, to boost performance, monitor progress, define goals, among other things. Consequently, the market for fitness systems (i.e. fitness applications) is expanding and is already very dense. However, the associated quality with such systems falls short both in terms of innovation and even crucial features. As a result, this dissertation proposes a solution - an innovative fitness system in the form of a mobile application allied with a powerful recommender system. The system is intended to provide a more individual and personalized experience to any type of fitness user through the offering of crucial features including the log and monitor of information, progress analysis, and also through innovative features such as the implementation of a recommender system capable of making fitness-related suggestions (i.e. training regimens or specific exercises) based on multiple factors like the user’s individual goals, characteristics, and history. Additionally, it should also provide a personal virtual assistant, where users can express their questions and doubts and have them answered instantly by a chatbot. During development, it was decided that a second recommender system was required to improve the system as a whole. This, the system, after being implemented, was evaluated and it can be concluded that the result was a success, having passed in all the defined metrics, except one, with average classifications of 4/5 on the satisfaction inquiries. The feedback obtained from the expert on the recommender system was highly useful and, in general, decently positive, having only a few questions that need improvement. Even though the intelligent recommender system couldn’t be tested with applicable data, the investigation and work done constitute a great asset in case there’s the opportunity to employ real data

Privacy-Protecting Techniques for Behavioral Data: A Survey

Our behavior (the way we talk, walk, or think) is unique and can be used as a biometric trait. It also correlates with sensitive attributes like emotions. Hence, techniques to protect individuals privacy against unwanted inferences are required. To consolidate knowledge in this area, we systematically reviewed applicable anonymization techniques. We taxonomize and compare existing solutions regarding privacy goals, conceptual operation, advantages, and limitations. Our analysis shows that some behavioral traits (e.g., voice) have received much attention, while others (e.g., eye-gaze, brainwaves) are mostly neglected. We also find that the evaluation methodology of behavioral anonymization techniques can be further improved