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Abstract

Previously, the main problem of information extraction was to gather enough data. Today, the challenge is not to collect data but to interpret and represent them in order to deduce information. Ontologies are considered suitable solutions for organizing information. The classic methods for ontology construction from textual documents rely on natural language analysis and are generally based on statistical or linguistic approaches. However, these approaches do not consider the document structure which provides additional knowledge. In fact, the structural organization of documents also conveys meaning. In this context, new approaches focus on document structure analysis to extract knowledge. This paper describes a methodology for ontology construction from web data and especially from Wikipedia articles. It focuses mainly on document structure in order to extract the main concepts and their relations. The proposed methods extract not only taxonomic and non-taxonomic relations but also give the labels describing non-taxonomic relations. The extraction of non-taxonomic relations is established by analyzing the titles hierarchy in each document. A pattern matching is also applied in order to extract known semantic relations. We propose also to apply a refinement to the extracted relations in order to keep only those that are relevant. The refinement process is performed by applying the transitive property, checking the nature of the relations and analyzing taxonomic relations having inverted arguments. Experiments have been performed on French Wikipedia articles related to the medical field. Ontology evaluation is performed by comparing it to gold standards.

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Abstract

Shiyali Ramamrita Ranganathan's theory of classification spans a number of works over a number of decades. And while he was devoted to solving many problems in the practice of librarianship, and is known as the father of library science in India (Garfield, 1984), his work in classification revolves around one central concern. His classification research addressed the problems that arose from introducing new ideas into a scheme for classification, while maintaining a meaningful hierarchical and systematically arranged order of classes. This is because hierarchical and systematically arranged classes are the defining characteristic of useful classification. To lose this order is to through the addition of new classes is to introduce confusion, if not chaos, and to move toward a useless classification - or at least one that requires complete revision. In the following chapter, I outline the stages, and the elements of those stages, in Ranganathan's thought on classification from 1926-1972, as well as posthumous work that continues his agenda. And while facets figure prominently in all of these stages; but for Ranganathan to achieve his goal, he must continually add to this central feature of his theory of classification. I will close this chapter with an outline of persistent problems that represent research fronts for the field. Chief among these are what to do about scheme change and the open question about the rigor of information modeling in light of semantic web developments.

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Date

12. 9.2004 17:22:35

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Date

7.11.2008 15:22:04

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Footnote

Essential Classification is also an exercise book. Indeed, it contains a number of practical exercises and activities in every chapter, along with suggested answers. Unfortunately, the answers are too often provided without the justifications and explanations that students would no doubt demand. The author has taken great care to explain all technical terms in her text, but formal definitions are also gathered in an extensive 172-term Glossary; appropriately, these terms appear in bold type the first time they are used in the text. A short, very short, annotated bibliography of standard classification textbooks and of manuals for the use of major classification schemes is provided. A detailed 11-page index completes the set of learning aids which will be useful to an audience of students in their effort to grasp the basic concepts of the theory and the practice of document classification in a traditional environment. Essential Classification is a fine textbook. However, this reviewer deplores the fact that it presents only a very "traditional" view of classification, without much reference to newer environments such as the Internet where classification also manifests itself in various forms. In Essential Classification, books are always used as examples, and we have to take the author's word that traditional classification practices and tools can also be applied to other types of documents and elsewhere than in the traditional library. Vanda Broughton writes, for example, that "Subject headings can't be used for physical arrangement" (p. 101), but this is not entirely true. Subject headings can be used for physical arrangement of vertical files, for example, with each folder bearing a simple or complex heading which is then used for internal organization. And if it is true that subject headings cannot be reproduced an the spine of [physical] books (p. 93), the situation is certainly different an the World Wide Web where subject headings as metadata can be most useful in ordering a collection of hot links. The emphasis is also an the traditional paperbased, rather than an the electronic version of classification schemes, with excellent justifications of course. The reality is, however, that supporting organizations (LC, OCLC, etc.) are now providing great quality services online, and that updates are now available only in an electronic format and not anymore on paper. E-based versions of classification schemes could be safely ignored in a theoretical text, but they have to be described and explained in a textbook published in 2005. One last comment: Professor Broughton tends to use the same term, "classification" to represent the process (as in classification is grouping) and the tool (as in constructing a classification, using a classification, etc.). Even in the Glossary where classification is first well-defined as a process, and classification scheme as "a set of classes ...", the definition of classification scheme continues: "the classification consists of a vocabulary (...) and syntax..." (p. 296-297). Such an ambiguous use of the term classification seems unfortunate and unnecessarily confusing in an otherwise very good basic textbook an categorization of concepts and subjects, document organization and subject representation."