Fusing Automatically Extracted Annotations for the Semantic Web

This research focuses on the problem of semantic data fusion. Although various solutions have been developed in the research communities focusing on databases and formal logic, the choice of an appropriate algorithm is non-trivial because the performance of each algorithm and its optimal configuration parameters depend on the type of data, to which the algorithm is applied. In order to be reusable, the fusion system must be able to select appropriate techniques and use them in combination. Moreover, because of the varying reliability of data sources and algorithms performing fusion subtasks, uncertainty is an inherent feature of semantically annotated data and has to be taken into account by the fusion system. Finally, the issue of schema heterogeneity can have a negative impact on the fusion performance. To address these issues, we propose KnoFuss: an architecture for Semantic Web data integration based on the principles of problem-solving methods. Algorithms dealing with different fusion subtasks are represented as components of a modular architecture, and their capabilities are described formally. This allows the architecture to select appropriate methods and configure them depending on the processed data. In order to handle uncertainty, we propose a novel algorithm based on the Dempster-Shafer belief propagation. KnoFuss employs this algorithm to reason about uncertain data and method results in order to refine the fused knowledge base. Tests show that these solutions lead to improved fusion performance. Finally, we addressed the problem of data fusion in the presence of schema heterogeneity. We extended the KnoFuss framework to exploit results of automatic schema alignment tools and proposed our own schema matching algorithm aimed at facilitating data fusion in the Linked Data environment. We conducted experiments with this approach and obtained a substantial improvement in performance in comparison with public data repositories

Efficient techniques for streaming cross document coreference resolution

Large text streams are commonplace; news organisations are constantly producing stories and people are constantly writing social media posts. These streams should be analysed in real-time so useful information can be extracted and acted upon instantly. When natural disasters occur people want to be informed, when companies announce new products financial institutions want to know and when celebrities do things their legions of fans want to feel involved. In all these examples people care about getting information in real-time (low latency). These streams are massively varied, people’s interests are typically classified by the entities they are interested in. Organising a stream by the entity being referred to would help people extract the information useful to them. This is a difficult task: fans of ‘Captain America’ films will not want to be incorrectly told that ‘Chris Evans’ (the main actor) was appointed to host ‘Top Gear’ when it was a different ‘Chris Evans’. People who use local idiosyncrasies such as referring to their home county (‘Cornwall’) as ‘Kernow’ (the Cornish for ‘Cornwall’ that has entered the local lexicon) should not be forced to change their language when finding out information about their home. This thesis addresses a core problem for real-time entity-specific NLP: Streaming cross document coreference resolution (CDC), how to automatically identify all the entities mentioned in a stream in real-time. This thesis address two significant problems for streaming CDC: There is no representative dataset and existing systems consume more resources over time. A new technique to create datasets is introduced and it was applied to social media (Twitter) to create a large (6M mentions) and challenging new CDC dataset that contains a much more variend range of entities than typical newswire streams. Existing systems are not able to keep up with large data streams. This problem is addressed with a streaming CDC system that stores a constant sized set of mentions. New techniques to maintain the sample are introduced significantly out-performing existing ones maintaining 95% of the performance of a non-streaming system while only using 20% of the memory

IDENTITY RESOLUTION IN EMAIL COLLECTIONS

Access to historically significant email collections poses challenges that arise less often in personal collections. Most notably, people exploring a large collection of emails, in which they were not sending or receiving, may not be very familiar with the discussions that exist in this collection. They would not only need to focus on understanding the topical content of those discussions, but would also find it useful to understand who the people sending, receiving, or mentioned in these discussions were. In this dissertation, the problem of resolving personal identity in the context of large email collections is tackled. In such collections, a common name (e.g., John) might easily refer to any one of several hundred people; when one of these people was mentioned in an email, the question then arises: "who is that John?'' To "resolve identity'' of people in an email collection, two problems need to be solved: (1) modeling the identity of the participants in that collection, and (2) resolving name-mentions (that appeared in the body of the messages) to these identities. To tackle the first problem, a simple computational model of identity, that is built on extracting unambiguous references (e.g., full names from headers, or nicknames from free-text signatures) to people from the whole collection, is presented. To tackle the second problem, a generative probabilistic approach that leverages the model of identity to resolve mentions is presented. The approach is motivated by intuitions about the way people might refer to others in an email; it expands the context surrounding a mention in four directions: the message where the mention was observed, the thread that includes that message, topically-related messages, and messages sent or received by the original communicating parties. It relies on less ambiguous references (e.g., email addresses or full names) that are observed in some context of a given mention to rank potential referents of that mention. In order to jointly resolve all mentions in the collection, a parallel implementation is presented using the MapReduce distributed-programming framework. The implementation decomposes the structure of the resolution process into subcomponents that fit the MapReduce task model well. At the heart of that implementation, a parallel algorithm for efficient computation of pairwise document similarity in large collections is proposed as a general solution that can be used for scalable context expansion of all mentions and other applications as well. The resolution approach compares favorably with previously-reported techniques on small test collections (sets of mention-queries that were manually resolved beforehand) that were used to evaluate the task in the literature. However, the mention-queries in those collections, besides being relatively few in number, are limited in that all refer to people for whom a substantial amount of evidence would be expected to be available in the collection thus omitting the "long tail'' of the identity distribution for which less evidence is available. This motivated the development of a new test collection that now is the largest and best-balanced test collection available for the task. To build this collection, a user study was conducted that also provided some insight into the difficulty of the task and how time-consuming it is when humans perform it, and the reliability of their task performance. The study revealed that at least 80% of the 584 annotated mentions were resolvable to people who had sent or received email within the same collection. The new test collection was used to experimentally evaluate the resolution system. The results highlight the importance of the social context (that includes messages sent or received by the original communicating parties) when resolving mentions in email. Moreover, the results show that combining evidence from multiple types of contexts yields better resolution than what can be achieved using any individual context. The one-best selection is correct 74% of the time when tested on the full set of the mention-queries, and 51% of the time when tested on the mention-queries labeled as "hard'' by the annotators. Experiments run with iterative reformulation of the resolution algorithm resulted in modest gains only for the second iteration in the social context expansion

A graph-based framework for data retrieved from criminal-related documents

A digitalização das empresas e dos serviços tem potenciado o tratamento e análise de um crescente volume de dados provenientes de fontes heterogeneas, com desafios emergentes, nomeadamente ao nível da representação do conhecimento. Também os Órgãos de Polícia Criminal (OPC) enfrentam o mesmo desafio, tendo em conta o volume de dados não estruturados, provenientes de relatórios policiais, sendo analisados manualmente pelo investigadores criminais, consumindo tempo e recursos. Assim, a necessidade de extrair e representar os dados não estruturados existentes em documentos relacionados com o crime, de uma forma automática, permitindo a redução da análise manual efetuada pelos investigadores criminais. Apresenta-se como um desafio para a ciência dos computadores, dando a possibilidade de propor uma alternativa computacional que permita extrair e representar os dados, adaptando ou propondo métodos computacionais novos. Actualmente existem vários métodos computacionais aplicados ao domínio criminal, nomeadamente a identificação e classificação de entidades nomeadas, por exemplo narcóticos, ou a extracção de relações entre entidades relevantes para a investigação criminal. Estes métodos são maioritariamente aplicadas à lingua inglesa, e em Portugal não há muita atenção à investigação nesta área, inviabilizando a sua aplicação no contexto da investigação criminal. Esta tese propõe uma solução integrada para a representação dos dados não estruturados existentes em documentos, usando um conjunto de métodos computacionais: Preprocessamento de Documentos, que agrupa uma tarefa de Extracção, Transformação e Carregamento adaptado aos documentos relacionados com o crime, seguido por um pipeline de Processamento de Linguagem Natural aplicado à lingua portuguesa, para uma análise sintática e semântica dos dados textuais; Método de Extracção de Informação 5W1H que agrupa métodos de Reconhecimento de Entidades Nomeadas, a detecção da função semântica e a extracção de termos criminais; Preenchimento da Base de Dados de Grafos e Enriquecimento, permitindo a representação dos dados obtidos numa base de dados de grafos Neo4j. Globalmente a solução integrada apresenta resultados promissores, cujos resultados foram validados usando protótipos desemvolvidos para o efeito. Demonstrou-se ainda a viabilidade da extracção dos dados não estruturados, a sua interpretação sintática e semântica, bem como a representação na base de dados de grafos; Abstract: The digitalization of companies processes has enhanced the treatment and analysis of a growing volume of data from heterogeneous sources, with emerging challenges, namely those related to knowledge representation. The Criminal Police has similar challenges, considering the amount of unstructured data from police reports manually analyzed by criminal investigators, with the corresponding time and resources. There is a need to automatically extract and represent the unstructured data existing in criminal-related documents and reduce the manual analysis by criminal investigators. Computer science faces a challenge to apply emergent computational models that can be an alternative to extract and represent the data using new or existing methods. A broad set of computational methods have been applied to the criminal domain, such as the identification and classification named-entities (NEs) or extraction of relations between the entities that are relevant for the criminal investigation, like narcotics. However, these methods have mainly been used in the English language. In Portugal, the research on this domain, applying computational methods, lacks related works, making its application in criminal investigation unfeasible. This thesis proposes an integrated solution for the representation of unstructured data retrieved from documents, using a set of computational methods, such as Preprocessing Criminal-Related Documents module. This module is supported by Extraction, Transformation, and Loading tasks. Followed by a Natural Language Processing pipeline applied to the Portuguese language, for syntactic and semantic analysis of textual data. Next, the 5W1H Information Extraction Method combines the Named-Entity Recognition, Semantic Role Labelling, and Criminal Terms Extraction tasks. Finally, the Graph Database Population and Enrichment allows us the representation of data retrieved into a Neo4j graph database. Globally, the framework presents promising results that were validated using prototypes developed for this purpose. In addition, the feasibility of extracting unstructured data, its syntactic and semantic interpretation, and the graph database representation has also been demonstrated

Grounding event references in news

Events are frequently discussed in natural language, and their accurate identification is central to language understanding. Yet they are diverse and complex in ontology and reference; computational processing hence proves challenging. News provides a shared basis for communication by reporting events. We perform several studies into news event reference. One annotation study characterises each news report in terms of its update and topic events, but finds that topic is better consider through explicit references to background events. In this context, we propose the event linking task which—analogous to named entity linking or disambiguation—models the grounding of references to notable events. It defines the disambiguation of an event reference as a link to the archival article that first reports it. When two references are linked to the same article, they need not be references to the same event. Event linking hopes to provide an intuitive approximation to coreference, erring on the side of over-generation in contrast with the literature. The task is also distinguished in considering event references from multiple perspectives over time. We diagnostically evaluate the task by first linking references to past, newsworthy events in news and opinion pieces to an archive of the Sydney Morning Herald. The intensive annotation results in only a small corpus of 229 distinct links. However, we observe that a number of hyperlinks targeting online news correspond to event links. We thus acquire two large corpora of hyperlinks at very low cost. From these we learn weights for temporal and term overlap features in a retrieval system. These noisy data lead to significant performance gains over a bag-of-words baseline. While our initial system can accurately predict many event links, most will require deep linguistic processing for their disambiguation

Grounding event references in news

Events are frequently discussed in natural language, and their accurate identification is central to language understanding. Yet they are diverse and complex in ontology and reference; computational processing hence proves challenging. News provides a shared basis for communication by reporting events. We perform several studies into news event reference. One annotation study characterises each news report in terms of its update and topic events, but finds that topic is better consider through explicit references to background events. In this context, we propose the event linking task which—analogous to named entity linking or disambiguation—models the grounding of references to notable events. It defines the disambiguation of an event reference as a link to the archival article that first reports it. When two references are linked to the same article, they need not be references to the same event. Event linking hopes to provide an intuitive approximation to coreference, erring on the side of over-generation in contrast with the literature. The task is also distinguished in considering event references from multiple perspectives over time. We diagnostically evaluate the task by first linking references to past, newsworthy events in news and opinion pieces to an archive of the Sydney Morning Herald. The intensive annotation results in only a small corpus of 229 distinct links. However, we observe that a number of hyperlinks targeting online news correspond to event links. We thus acquire two large corpora of hyperlinks at very low cost. From these we learn weights for temporal and term overlap features in a retrieval system. These noisy data lead to significant performance gains over a bag-of-words baseline. While our initial system can accurately predict many event links, most will require deep linguistic processing for their disambiguation