Thesis (M.S.)--State University of New York at Binghamton, Dept. of Computer Science, 2006. / Includes bibliographical references.

Thesis (Ph. D.)--George Mason University, 2008. / Vita: p. 177. Thesis director: Larry Kerschberg. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Information Technology. Title from PDF t.p. (viewed July 3, 2008). Includes bibliographical references (p. 169-176). Also issued in print.

Module extraction is an important reasoning task, aiding in the design, reuse and maintenance of ontologies. Reasoning services such as subsumption testing and MinA extraction have been shown to bene t from module extraction methods. Though various syntactic traversal-based module extraction algorithms exist for extracting modules, many only consider the subsumee of a subsumption statement as a selection criterion for reducing the axioms in the module. In this dissertation we extend the bottom-up reachability-based module extraction heuristic for the inexpressive Description Logic EL, by introducing a top-down version of the heuristic which utilises the subsumer of a subsumption statement as a selection criterion to minimize the number of axioms in a module. Then a combined bidirectional heuristic is introduced which uses both operands of a subsumption statement in order to extract very small modules. We then investigate the relationship between MinA extraction and bidirectional reachabilitybased module extraction. We provide empirical evidence that bidirectional reachability-based module extraction for subsumption entailments in EL provides a signi cant reduction in the size of modules for almost no additional costs in the running time of the original algorithms. / Computer Science / M. Sc. (Computer Science)

Module extraction is an important reasoning task, aiding in the design, reuse and maintenance of ontologies. Reasoning services such as subsumption testing and MinA extraction have been shown to bene t from module extraction methods. Though various syntactic traversal-based module extraction algorithms exist for extracting modules, many only consider the subsumee of a subsumption statement as a selection criterion for reducing the axioms in the module. In this dissertation we extend the bottom-up reachability-based module extraction heuristic for the inexpressive Description Logic EL, by introducing a top-down version of the heuristic which utilises the subsumer of a subsumption statement as a selection criterion to minimize the number of axioms in a module. Then a combined bidirectional heuristic is introduced which uses both operands of a subsumption statement in order to extract very small modules. We then investigate the relationship between MinA extraction and bidirectional reachabilitybased module extraction. We provide empirical evidence that bidirectional reachability-based module extraction for subsumption entailments in EL provides a signi cant reduction in the size of modules for almost no additional costs in the running time of the original algorithms. / Computer Science / M. Sc. (Computer Science)

Orientador: Walter Moreira / Banca: Edberto Ferneda / Banca: Rogério Aparecido Sá Ramalho / Resumo: Aborda sobre as relações conceituais que se mostram presentes em todos os sistemas de organização do conhecimento. Ao organizar o conhecimento, delimita-se classes e cada classe desempenha relações com outras classes. Neste contexto, inserem-se a Classificação Decimal de Dewey (CDD) e as ontologias como forma de organizar o conhecimento físico e digital, respectivamente. Partindo-se do pressuposto de que os sistemas de organização do conhecimento se complementam, o objetivo geral desta pesquisa é o de comparar o modelo das relações conceituais presentes nos sistemas de classificação com o modelo de relações conceituais presentes nas ontologias. Para tanto, tomou-se como objeto de análise a classe 590 da CDD sobre Animais, e a BBC Wildlife Ontology e, assim, foram definidos como objetivos específicos: Compreender os tipos de relações conceituais e suas características; Analisar as relações conceituais da classe 590 da CDD; Investigar a consistência das relações conceituais na BBC Wildlife Ontology; Realizar análise comparativa sobre os tipos de relações conceituais identificados na CDD e na BBC Wildlife Ontology; Criar um modelo de ontologia que sintetize os dois sistemas de organização do conhecimento analisados para fins de sistematização. Para a realização desses objetivos adotou-se, em síntese, os seguintes procedimentos metodológicos: 1) coleta de dados a partir da literatura da área; 2) análise das relações conceituais da classe 590 da CDD; 3) análise das relações concei... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: It deals with the conceptual relations that are present in all Knowledge Organization Systems. When knowledge is organized, classes are delimited and each class performs relationships with other classes. The Dewey Decimal Classification (CDD) and the ontologies are inserted in this context as a way of organizing the physical and digital knowledge, respectively. Assuming that the Knowledge Systems Organization complement each other, the general objective of this research is to compare the model of the conceptual relations present in the classification systems with the model of conceptual relations present in the ontologies. Therefore, the CDD class 590 about Animals and the BBC Wildlife Ontology were taken as the object of analysis and thus were defined as specific objectives. To understand the types of conceptual relationships and their characteristics; to analyze the conceptual relationships of class 590 of the CDD; To investigate the consistency of conceptual relationships in the BBC Wildlife Ontology; To conduct a comparative analysis of the types of conceptual relationships identified in the CDD and the BBC Wildlife Ontology; To create an ontology model that synthesizes the two Knowledge Organization Systems analyzed for systematization purposes. In order to achieve these objectives, the following methodological procedures were adopted: 1) data collection from the literature of the area; 2) analysis of the conceptual relationships of class 590 from CDD; 3) analysis of con... (Complete abstract click electronic access below) / Mestre

Thesis (M.S.)--California Polytechnic State University, 2009. / Title from PDF title page; viewed on Apr. 21, 2009. "March, 2009." "In partial fulfillment of the requirements for the degree [of] Master of Science in Computer Science." "Presented to the faculty of California Polytechnic State University, San Luis Obispo." Major professor: Franz Kurfess, Ph. D. Includes bibliographical references (p. 40-42). Also available on microfiche.

Thesis (Ph. D.)--University of Florida, 2005. / Title from title page of source document. Document formatted into pages; contains 126 pages. Includes vita. Includes bibliographical references.

xiii, 149 p. : ill. (some col.) / Information extraction (IE) aims to recognize and retrieve certain types of information from natural language text. For instance, an information extraction system may extract key geopolitical indicators about countries from a set of web pages while ignoring other types of information. IE has existed as a research field for a few decades, and ontology-based information extraction (OBIE) has recently emerged as one of its subfields. Here, the general idea is to use ontologies--which provide formal and explicit specifications of shared conceptualizations--to guide the information extraction process. This dissertation presents two novel directions for ontology-based information extraction in which ontologies are used to improve the information extraction process. First, I describe how a component-based approach for information extraction can be designed through the use of ontologies in information extraction. A key idea in this approach is identifying components of information extraction systems which make extractions with respect to specific ontological concepts. These components are termed "information extractors". The component-based approach explores how information extractors as well as other types of components can be used in developing information extraction systems. This approach has the potential to make a significant contribution towards the widespread usage and commercialization of information extraction. Second, I describe how an ontology-based information extraction system can make use of multiple ontologies. Almost all previous systems use a single ontology, although multiple ontologies are available for most domains. Using multiple ontologies in information extraction has the potential to extract more information from text and thus leads to an improvement in performance measures. The concept of information extractor, conceived in the component-based approach for information extraction, is used in designing the principles for accommodating multiple ontologies in an ontology-based information extraction system. / Committee in charge: Dr. Dejing Dou, Chair; Dr. Arthur Farley, Member; Dr. Michal Young, Member; Dr. Monte Westerfield, Outside Member

Orientador: Edberto Ferneda / Banca: Maria José Vicentini Jorente / Banca: Luciana Maria Vieira Pöttker / Resumo: Um sistema de recuperação de informação é um elemento mediador entre um acervo documental e os usuários que buscam por documentos relevantes. Nesse contexto, as interfaces desempenham uma função importante: em um primeiro momento, auxiliando o usuário na tarefa de expressar a sua necessidade de informação por meio de uma expressão de busca e, em um segundo momento, fornecendo recursos para ajudá-lo a selecionar documentos relevantes dentre os resultados obtidos. A recuperação de informação é um processo linguístico cuja eficiência depende de coincidências terminológicas entre a expressão de busca do usuário e a representação dos documentos. Este trabalho propõe um modelo de interface na qual a estrutura terminológica de uma ontologia é utilizada para auxiliar o usuário na seleção de documentos relevantes dentre aqueles resultantes de sua busca. Caracteriza-se como uma pesquisa de natureza aplicada, e exploratória e bibliográfica quanto aos procedimentos. Conclui-se que a apresentação visual de uma ontologia permite o desenvolvimento de interfaces dinâmicas e interativas, proporcionando ao usuário uma navegação estimulante e prazerosa por entre os documentos resultantes de sua busca, tendo por base os termos de uma determinada área de conhecimento. / Abstract: An information retrieval system is a mediating element between a document collection and the users who looking for relevant documents. In this context, interfaces play an important role: firstly, assisting the user to expressing their information need by means of a search expression, and secondly by providing resources to help selecting relevant documents from the obtained results. The information retrieval is a linguistic process whose efficiency depends on terminological coincidences between the user's query and the representation of documents. This work proposes an interface model in which the terminological structure of an ontology is used to assist the user in the selection of relevant documents among those resulting from their search. It is characterized as an applied, exploratory and bibliographic research. It is concluded that the visual presentation of ontology allows the development of dynamic and interactive interfaces, providing the user with stimulating and pleasant navigation among the documents resulting from their search, based on the terms of a certain knowledge area. / Mestre

The Semantic Web, as the foreseen successor of the current Web, is envisioned to be a semantically enriched information space usable by machines or agents that perform sophisticated tasks on behalf of their users. The realisation of the Semantic Web prescribe the development of a comprehensive and functional layered architecture for the increasingly semantically expressive languages that it comprises of. A functional architecture is a model specified at an appropriate level of abstraction identifying system components based on required system functionality, whilst a comprehensive architecture is an architecture founded on established design principles within Software Engineering. Within this study, an argument is formulated for the development of a comprehensive and functional layered architecture through the development of a Semantic Web status model, the extraction of the function of established Semantic Web technologies, as well as the development of an evaluation mechanism for layered architectures compiled from design principles as well as fundamental features of layered architectures. In addition, an initial version of such a comprehensive and functional layered architecture for the Semantic Web is constructed based on the building blocks described above, and this architecture is applied to several scenarios to establish the usefulness thereof. In conclusion, based on the evidence collected as result of the research in this study, it is possible to justify the development of an architectural model, or more specifically, a comprehensive and functional layered architecture for the languages of the Semantic Web. / Computing / PHD (Computer Science)