Improving dental care recommendation systems using trust and social networks

The growing popularity of Health Social Networking sites has a tremendous impact on people's health related experiences. However, without any quality filtering, there could be a detrimental effect on the users' health. Trust-based techniques have been identified as effective methods to filter the information for recommendation systems. This research focuses on dental care related social networks and recommendation systems. Trust is critical when choosing a dental care provider due to the invasive nature of the treatment. Surprisingly, current dental care recommendation systems do not use trust-based techniques, and most of them are simple reviews and ratings sites. This research aims at improving dental care recommendation systems by proposing a new framework, taking trust into account. It derives trust from both users' social networks and from existing crowdsourced information on dental care. Such a framework could be used for other healthcare recommendation systems where trust is of major importance. © 2014 IEEE

Análise de tipos de ontologias nas áreas de ciência da informação e ciência da computação

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências da Educação, Programa de Pós-Graduação em Ciência da Informação, Florianópolis, 2014.A emergência de tecnologias que visam complementar a web, associada às problemáticas na busca por novos modelos de recuperação de informação mais eficientes, abriram espaço para estudos que utilizam os benefícios da organização semântica da informação e do conhecimento. Sistemas de Organização do Conhecimento (SOCs) permitem representar um domínio por meio da sistematização dos conceitos e das relações semânticas que se estabelecem entre eles. Entre os tipos desses sistemas conceituais estão as ontologias, utilizadas para representar o conhecimento relativo a um dado domínio do conhecimento. A presente pesquisa tem como objetivo, por meio de uma pesquisa documental, identificar as principais características dos tipos de ontologias. Para tanto, foi empregado, nos procedimentos metodológicos, o método de Análise de Conteúdo de Laurence Bardin. Para a construção do corpus de análise foram utilizadas as bases de dados da Library and Information Science Abstracts (LISA) e da Computer and Information Systems Abstracts. A análise dos resultados permitiu identificar um predomínio significativo nas pesquisas relacionadas às ontologias de domínio, utilizando-a como ferramenta para representação de conceitos e relações que estejam inseridas na visão de mundo desejada. Diferentemente, as ontologias de topo definem os conceitos mais básicos e que sejam extensíveis a outras ações e domínios associados a sua área de abordagem. Os tipos aplicação e tarefa permitem um nível de representação mais específico, alinhado a modelagem de ambientes particulares.Abstract : The emergence of technologies that aim at complementing the internet, associated with the problematics that arise in the search for new models of information retrieval that are more efficient, have made room for studies that make use of the benefits of the semantic organization of information and knowledge. Knowledge Organization Systems (KOS) allow the representation of a domain through the systematization of concepts and semantic relations that have been stablished between them. Among these forms of conceptual systems are the ontologies, utilized in the representation of knowledge relative to a given knowledge domain. The goal of this research, therefore, is to identify the main characteristics of the types of ontologies through documentary research. For that, we have employed in the methodological procedures the Laurence Bardin Content Analysis Method. As for the corpus analysis construction we made use of the databases of the Library and Information Science Abstracts (LISA) and Computer and Information Systems Abstracts. The analysis of the results allowed the identification of a significant predominance of researches related to domain ontologies, they were used as tools for the representation of concepts and relations that are inserted in the desired world view. In contrast, top level ontologies define the most basic concepts that are extendable to other actions and domains associated to its approach area. The application and task types allow a representation that is more specific and alligned with the modeling of particular environments

Towards Time-Aware Context-Aware Deep Trust Prediction in Online Social Networks

Trust can be defined as a measure to determine which source of information is reliable and with whom we should share or from whom we should accept information. There are several applications for trust in Online Social Networks (OSNs), including social spammer detection, fake news detection, retweet behaviour detection and recommender systems. Trust prediction is the process of predicting a new trust relation between two users who are not currently connected. In applications of trust, trust relations among users need to be predicted. This process faces many challenges, such as the sparsity of user-specified trust relations, the context-awareness of trust and changes in trust values over time. In this dissertation, we analyse the state-of-the-art in pair-wise trust prediction models in OSNs. We discuss three main challenges in this domain and present novel trust prediction approaches to address them. We first focus on proposing a low-rank representation of users that incorporates users' personality traits as additional information. Then, we propose a set of context-aware trust prediction models. Finally, by considering the time-dependency of trust relations, we propose a dynamic deep trust prediction approach. We design and implement five pair-wise trust prediction approaches and evaluate them with real-world datasets collected from OSNs. The experimental results demonstrate the effectiveness of our approaches compared to other state-of-the-art pair-wise trust prediction models.Comment: 158 pages, 20 figures, and 19 tables. This is my PhD thesis in Macquarie University, Sydney, Australi

Detection of suspicious URLs in online social networks using supervised machine learning algorithms

This thesis proposes the use of several supervised machine learning classification models that were built to detect the distribution of malicious content in OSNs. The main focus was on ensemble learning algorithms such as Random Forest, gradient boosting trees, extra trees, and XGBoost. Features were used to identify social network posts that contain malicious URLs derived from several sources, such as domain WHOIS record, web page content, URL lexical and redirection data, and Twitter metadata. The thesis describes a systematic analysis of the hyper-parameters of tree-based models. The impact of key parameters, such as the number of trees, depth of trees and minimum size of leaf nodes on classification performance, was assessed. The results show that controlling the complexity of Random Forest classifiers applied to social media spam is essential to avoid overfitting and optimise performance. The model complexity could be reduced by removing uninformative features, as the complexity they add to the model is greater than the advantages they give to the model to make decisions. Moreover, model-combining methods were tested, which are the voting and stacking methods. Both show advantages and disadvantages; however, in general, they appear to provide a statistically significant improvement in comparison to the highest singular model. The critical benefit of applying the stacking method to automate the model selection process is that it is effective in giving more weight to more topperforming models and less affected by weak ones. Finally, 'SuspectRate', an online malicious URL detection system, was built to offer a service to give a suspicious probability of tweets with attached URLs. A key feature of this system is that it can dynamically retrain and expand current models