Combating Misinformation on Social Media by Exploiting Post and User-level Information

Misinformation on social media has far-reaching negative impact on the public and society. Given the large number of real-time posts on social media, traditional manual-based methods of misinformation detection are not viable. Therefore, computational approaches (i.e., data-driven) have been proposed to combat online misinformation. Previous work on computational misinformation analysis has mainly focused on employing natural language processing (NLP) techniques to develop misinformation detection systems at the post level (e.g., using text and propagation network). However, it is also important to exploit information at the user level in social media, as users play a significant role (e.g., post, diffuse, refute, etc.) in spreading misinformation. The main aim of this thesis is to: (i) develop novel methods for analysing the behaviour of users who are likely to share or refute misinformation in social media; and (ii) predict and characterise unreliable stories with high popularity in social media. To this end, we first highlight the limitations in the evaluation protocol in popular rumour detection benchmarks on the post level and propose to evaluate such systems using chronological splits (i.e., considering temporal concept drift). On the user level, we introduce two novel tasks on (i) early detecting Twitter users that are likely to share misinformation before they actually do it; and (ii) identifying and characterising active citizens who refute misinformation in social media. Finally, we develop a new dataset to enable the study on predicting the future popularity (e.g. number of likes, replies, retweets) of false rumour on Weibo

Geographic information extraction from texts

A large volume of unstructured texts, containing valuable geographic information, is available online. This information – provided implicitly or explicitly – is useful not only for scientific studies (e.g., spatial humanities) but also for many practical applications (e.g., geographic information retrieval). Although large progress has been achieved in geographic information extraction from texts, there are still unsolved challenges and issues, ranging from methods, systems, and data, to applications and privacy. Therefore, this workshop will provide a timely opportunity to discuss the recent advances, new ideas, and concepts but also identify research gaps in geographic information extraction

Implicit Entity Networks: A Versatile Document Model

The time in which we live is often referred to as the Information Age. However, it can also aptly be characterized as an age of constant information overload. Nowhere is this more present than on the Web, which serves as an endless source of news articles, blog posts, and social media messages. Of course, this overload is even greater in professions that handle the creation or extraction of information and knowledge, such as journalists, lawyers, researchers, clerks, or medical professionals. The volume of available documents and the interconnectedness of their contents are both a blessing and a curse for the contemporary information consumer. On the one hand, they provide near limitless information, but on the other hand, their consumption and comprehension requires an amount of time that many of us cannot spare. As a result, automated extraction, aggregation, and summarization techniques have risen in popularity, even though they are a long way from being comprehensive. When we, as humans, are faced with an overload of information, we tend to look for patterns that bring order into the chaos. In news, we might identify familiar political figures or celebrities, whereas we might look for expressive symptoms in medicine, or precedential cases in law. In other words, we look for known entities as reference points, and then explore the content along the lines of their relations to others entities. Unfortunately, this approach is not reflected in current document models, which do not provide a similar focus on entities. As a direct result, the retrieval of entity-centric knowledge and relations from a flood of textual information becomes more difficult than it has to be, and the inclusion of external knowledge sources is impeded. In this thesis, we introduce implicit entity networks as a comprehensive document model that addresses this shortcoming and provides a holistic representation of document collections and document streams. Based on the premise of modelling the cooccurrence relations between terms and entities as first-class citizens, we investigate how the resulting network structure facilitates efficient and effective entity-centric search, and demonstrate the extraction of complex entity relations, as well as their summarization. We show that the implicit network model is fully compatible with dynamic streams of documents. Furthermore, we introduce document aggregation methods that are sensitive to the context of entity mentions, and can be used to distinguish between different entity relations. Beyond the relations of individual entities, we introduce network topics as a novel and scalable method for the extraction of topics from collections and streams of documents. Finally, we combine the insights gained from these applications in a versatile hypergraph document model that bridges the gap between unstructured text and structured knowledge sources

Exploiting multiple sources of evidence for opinion search in the web

In this thesis we study Opinion Mining and Sentiment Analysis and propose a ne-grained analysis of the opinions conveyed in texts. Concretely, the aim of this research is to gain an understanding on how to combine di erent types of evidence to e ectively determine on-topic opinions in texts. To meet this aim, we consider content-match evidence, obtained at document and passage level, as well as di erent structural aspects of the text. Current Opinion Mining technology is not mature yet. As a matter of fact, people often use regular search engines, which lack evolved opinion search ca- pabilities, to nd opinions about their interests. This means that the e ort of detecting what are the key relevant opinions relies on the user. The lack of widely accepted Opinion Mining technology is due to the limitations of cur- rent models, which are simplistic and perform poorly. In this thesis we study a speci c set of factors that are indicative of subjectivity and relevance and we try to understand how to e ectively combine them to detect opinionated docu- ments, to extract relevant opinions and to estimate their polarity. We propose innovative methods and models able to incorporate di erent types of evidence and it is our intention to contribute in di erent areas, including those related to i) search for opinionated documents, ii) detection of subjectivity at docu- ment and passage level, and iii) estimation of polarity. An important concern that guides this research is e ciency. Some types of evidence, such as discourse structure, have only been tested with small collections from narrow domains (e.g., movie reviews). We demonstrate here that evolved linguistic features { based on discourse analysis{ can potentially lead to a better understanding of how subjectivity ows in texts. And we show that this type of features can be e ciently injected into general-purpose opinion retrieval solutions that operate at large scale

Políticas de Copyright de Publicações Científicas em Repositórios Institucionais: O Caso do INESC TEC

A progressiva transformação das práticas científicas, impulsionada pelo desenvolvimento das novas Tecnologias de Informação e Comunicação (TIC), têm possibilitado aumentar o acesso à informação, caminhando gradualmente para uma abertura do ciclo de pesquisa. Isto permitirá resolver a longo prazo uma adversidade que se tem colocado aos investigadores, que passa pela existência de barreiras que limitam as condições de acesso, sejam estas geográficas ou financeiras. Apesar da produção científica ser dominada, maioritariamente, por grandes editoras comerciais, estando sujeita às regras por estas impostas, o Movimento do Acesso Aberto cuja primeira declaração pública, a Declaração de Budapeste (BOAI), é de 2002, vem propor alterações significativas que beneficiam os autores e os leitores. Este Movimento vem a ganhar importância em Portugal desde 2003, com a constituição do primeiro repositório institucional a nível nacional. Os repositórios institucionais surgiram como uma ferramenta de divulgação da produção científica de uma instituição, com o intuito de permitir abrir aos resultados da investigação, quer antes da publicação e do próprio processo de arbitragem (preprint), quer depois (postprint), e, consequentemente, aumentar a visibilidade do trabalho desenvolvido por um investigador e a respetiva instituição. O estudo apresentado, que passou por uma análise das políticas de copyright das publicações científicas mais relevantes do INESC TEC, permitiu não só perceber que as editoras adotam cada vez mais políticas que possibilitam o auto-arquivo das publicações em repositórios institucionais, como também que existe todo um trabalho de sensibilização a percorrer, não só para os investigadores, como para a instituição e toda a sociedade. A produção de um conjunto de recomendações, que passam pela implementação de uma política institucional que incentive o auto-arquivo das publicações desenvolvidas no âmbito institucional no repositório, serve como mote para uma maior valorização da produção científica do INESC TEC.The progressive transformation of scientific practices, driven by the development of new Information and Communication Technologies (ICT), which made it possible to increase access to information, gradually moving towards an opening of the research cycle. This opening makes it possible to resolve, in the long term, the adversity that has been placed on researchers, which involves the existence of barriers that limit access conditions, whether geographical or financial. Although large commercial publishers predominantly dominate scientific production and subject it to the rules imposed by them, the Open Access movement whose first public declaration, the Budapest Declaration (BOAI), was in 2002, proposes significant changes that benefit the authors and the readers. This Movement has gained importance in Portugal since 2003, with the constitution of the first institutional repository at the national level. Institutional repositories have emerged as a tool for disseminating the scientific production of an institution to open the results of the research, both before publication and the preprint process and postprint, increase the visibility of work done by an investigator and his or her institution. The present study, which underwent an analysis of the copyright policies of INESC TEC most relevant scientific publications, allowed not only to realize that publishers are increasingly adopting policies that make it possible to self-archive publications in institutional repositories, all the work of raising awareness, not only for researchers but also for the institution and the whole society. The production of a set of recommendations, which go through the implementation of an institutional policy that encourages the self-archiving of the publications developed in the institutional scope in the repository, serves as a motto for a greater appreciation of the scientific production of INESC TEC

Applying insights from machine learning towards guidelines for the detection of text-based fake news

Web-based technologies have fostered an online environment where information can be disseminated in a fast and cost-effective manner whilst targeting large and diverse audiences. Unfortunately, the rise and evolution of web-based technologies have also created an environment where false information, commonly referred to as “fake news”, spreads rapidly. The effects of this spread can be catastrophic. Finding solutions to the problem of fake news is complicated for a myriad of reasons, such as: what is defined as fake news, the lack of quality datasets available to researchers, the topics covered in such data, and the fact that datasets exist in a variety of languages. The effects of false information dissemination can result in reputational damage, financial damage to affected brands, and ultimately, misinformed online news readers who can make misinformed decisions. The objective of the study is to propose a set of guidelines that can be used by other system developers to implement misinformation detection tools and systems. The guidelines are constructed using findings from the experimentation phase of the project and information uncovered in the literature review conducted as part of the study. A selection of machine and deep learning approaches are examined to test the applicability of cues that could separate fake online articles from real online news articles. Key performance metrics such as precision, recall, accuracy, F1-score, and ROC are used to measure the performance of the selected machine learning and deep learning models. To demonstrate the practicality of the guidelines and allow for reproducibility of the research, each guideline provides background information relating to the identified problem, a solution to the problem through pseudocode, code excerpts using the Python programming language, and points of consideration that may assist with the implementation.Thesis (MA) --Faculty of Engineering, the Built Environment, and Technology, 202

Applying insights from machine learning towards guidelines for the detection of text-based fake news

Web-based technologies have fostered an online environment where information can be disseminated in a fast and cost-effective manner whilst targeting large and diverse audiences. Unfortunately, the rise and evolution of web-based technologies have also created an environment where false information, commonly referred to as “fake news”, spreads rapidly. The effects of this spread can be catastrophic. Finding solutions to the problem of fake news is complicated for a myriad of reasons, such as: what is defined as fake news, the lack of quality datasets available to researchers, the topics covered in such data, and the fact that datasets exist in a variety of languages. The effects of false information dissemination can result in reputational damage, financial damage to affected brands, and ultimately, misinformed online news readers who can make misinformed decisions. The objective of the study is to propose a set of guidelines that can be used by other system developers to implement misinformation detection tools and systems. The guidelines are constructed using findings from the experimentation phase of the project and information uncovered in the literature review conducted as part of the study. A selection of machine and deep learning approaches are examined to test the applicability of cues that could separate fake online articles from real online news articles. Key performance metrics such as precision, recall, accuracy, F1-score, and ROC are used to measure the performance of the selected machine learning and deep learning models. To demonstrate the practicality of the guidelines and allow for reproducibility of the research, each guideline provides background information relating to the identified problem, a solution to the problem through pseudocode, code excerpts using the Python programming language, and points of consideration that may assist with the implementation.Thesis (MA) --Faculty of Engineering, the Built Environment, and Technology, 202