Search (7 results, page 1 of 1)

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Date

26. 9.2006 21:00:22

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Date

26.12.2011 13:22:07

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Source

Wissensspeicher in digitalen Räumen: Nachhaltigkeit - Verfügbarkeit - semantische Interoperabilität. Proceedings der 11. Tagung der Deutschen Sektion der Internationalen Gesellschaft für Wissensorganisation, Konstanz, 20. bis 22. Februar 2008. Hrsg.: J. Sieglerschmidt u. H.P.Ohly

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Abstract

T.1: Today's thesauri are mostly electronic tools, having moved on from the paper-based era when thesaurus standards were first developed. They are built and maintained with the support of software and need to integrate with other software, such as search engines and content management systems. Whereas in the past thesauri were designed for information professionals trained in indexing and searching, today there is a demand for vocabularies that untrained users will find to be intuitive. ISO 25964 makes the transition needed for the world of electronic information management. However, part 1 retains the assumption that human intellect is usually involved in the selection of indexing terms and in the selection of search terms. If both the indexer and the searcher are guided to choose the same term for the same concept, then relevant documents will be retrieved. This is the main principle underlying thesaurus design, even though a thesaurus built for human users may also be applied in situations where computers make the choices. Efficient exchange of data is a vital component of thesaurus management and exploitation. Hence the inclusion in this standard of recommendations for exchange formats and protocols. Adoption of these will facilitate interoperability between thesaurus management systems and the other computer applications, such as indexing and retrieval systems, that will utilize the data. Thesauri are typically used in post-coordinate retrieval systems, but may also be applied to hierarchical directories, pre-coordinate indexes and classification systems. Increasingly, thesaurus applications need to mesh with others, such as automatic categorization schemes, free-text search systems, etc. Part 2 of ISO 25964 describes additional types of structured vocabulary and gives recommendations to enable interoperation of the vocabularies at all stages of the information storage and retrieval process.
T.2: The ability to identify and locate relevant information among vast collections and other resources is a major and pressing challenge today. Several different types of vocabulary are in use for this purpose. Some of the most widely used vocabularies were designed a hundred years ago and have been evolving steadily. A different generation of vocabularies is now emerging, designed to exploit the electronic media more effectively. A good understanding of the previous generation is still essential for effective access to collections indexed with them. An important object of ISO 25964 as a whole is to support data exchange and other forms of interoperability in circumstances in which more than one structured vocabulary is applied within one retrieval system or network. Sometimes one vocabulary has to be mapped to another, and it is important to understand both the potential and the limitations of such mappings. In other systems, a thesaurus is mapped to a classification scheme, or an ontology to a thesaurus. Comprehensive interoperability needs to cover the whole range of vocabulary types, whether young or old. Concepts in different vocabularies are related only in that they have the same or similar meaning. However, the meaning can be found in a number of different aspects within each particular type of structured vocabulary: - within terms or captions selected in different languages; - in the notation assigned indicating a place within a larger hierarchy; - in the definition, scope notes, history notes and other notes that explain the significance of that concept; and - in explicit relationships to other concepts or entities within the same vocabulary. In order to create mappings from one structured vocabulary to another it is first necessary to understand, within the context of each different type of structured vocabulary, the significance and relative importance of each of the different elements in defining the meaning of that particular concept. ISO 25964-1 describes the key characteristics of thesauri along with additional advice on best practice. ISO 25964-2 focuses on other types of vocabulary and does not attempt to cover all aspects of good practice. It concentrates on those aspects which need to be understood if one of the vocabularies is to work effectively alongside one or more of the others. Recognizing that a new standard cannot be applied to some existing vocabularies, this part of ISO 25964 provides informative description alongside the recommendations, the aim of which is to enable users and system developers to interpret and implement the existing vocabularies effectively. The remainder of ISO 25964-2 deals with the principles and practicalities of establishing mappings between vocabularies.

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Abstract

The paper analysed here is a kind of position paper. In order to get a better under-standing of the reported work I used the retrieval interface of the thesaurus, the so-called NCI DTS Browser accessible via the Web3, and I perused the cited OWL file4 with numerous "Find" and "Find next" string searches. In addition the file was im-ported into Protégé 2000, Release 2.0, with OWL Plugin 1.0 and Racer Plugin 1.7.14. At the end of the paper's introduction the authors say: "In the following sections, this paper will describe the terminology development process at NCI, and the issues associated with converting a description logic based nomenclature to a semantically rich OWL ontology." While I will not deal with the first part, i.e. the terminology development process at NCI, I do not see the thesaurus as a description logic based nomenclature, or its cur-rent state and conversion already result in a "rich" OWL ontology. What does "rich" mean here? According to my view there is a great quantity of concepts and links but a very poor description logic structure which enables inferences. And what does the fol-lowing really mean, which is said a few lines previously: "Although editors have defined a number of named ontologic relations to support the description-logic based structure of the Thesaurus, additional relation-ships are considered for inclusion as required to support dependent applications."
According to my findings several relations available in the thesaurus query interface as "roles", are not used, i.e. there are not yet any assertions with them. And those which are used do not contribute to complete concept definitions of concepts which represent thesaurus main entries. In other words: The authors claim to already have a "description logic based nomenclature", where there is not yet one which deserves that title by being much more than a thesaurus with strict subsumption and additional inheritable semantic links. In the last section of the paper the authors say: "The most time consuming process in this conversion was making a careful analysis of the Thesaurus to understand the best way to translate it into OWL." "For other conversions, these same types of distinctions and decisions must be made. The expressive power of a proprietary encoding can vary widely from that in OWL or RDF. Understanding the original semantics and engineering a solution that most closely duplicates it is critical for creating a useful and accu-rate ontology." My question is: What decisions were made and are they exemplary, can they be rec-ommended as "the best way"? I raise strong doubts with respect to that, and I miss more profound discussions of the issues at stake. The following notes are dedicated to a critical description and assessment of the results of that conversion activity. They are written in a tutorial style more or less addressing students, but myself being a learner especially in the field of medical knowledge representation I do not speak "ex cathedra".

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Abstract

LCSH is known as such since 1975. It always has created headings to serve the LC collections instead of a theoretical basis. It started to replace cross reference codes by thesaural codes in 1986, in a mechanical fashion. It was in no way transformed into a thesaurus. Its encyclopedic coverage, its pre-coordinate concepts make it substantially distinct, considering that thesauri usually map a restricted field of knowledge and use uniterms. The questions raised are whether the new symbols comply with thesaurus standards and if they are true to one or to several models. Explanations and definitions from other lists of subject headings and thesauri, literature in the field of classification and subject indexing will provide some answers. For instance, see refers from a subject heading not used to another or others used. Exceptionally it will lead from a specific term to a more general one. Some equate a see reference with the equivalence relationship. Such relationships are pointed by USE in LCSH. See also references are made from the broader subject to narrower parts of it and also between associated subjects. They suggest lateral or vertical connexions as well as reciprocal relationships. They serve a coordination purpose for some, lay down a methodical search itinerary for others. Since their inception in the 1950's thesauri have been devised for indexing and retrieving information in the fields of science and technology. Eventually they attended to a number of social sciences and humanities. Research derived from thesauri was voluminous. Numerous guidelines are designed. They did not discriminate between the "hard" sciences and the social sciences. RT relationships are widely but diversely used in numerous controlled vocabularies. LCSH's aim is to achieve a list almost free of RT and SA references. It thus restricts relationships to BT/NT, USE and UF. This raises the question as to whether all fields of knowledge can "fit" in the Procrustean bed of RT/NT, i.e., genus/species relationships. Standard codes were devised. It was soon realized that BT/NT, well suited to the genus/species couple could not signal a whole-part relationship. In LCSH, BT and NT function as reciprocals, the whole-part relationship is taken into account by ISO. It is amply elaborated upon by authors. The part-whole connexion is sometimes studied apart. The decision to replace cross reference codes was an improvement. Relations can now be distinguished through the distinct needs of numerous fields of knowledge are not attended to. Topic inclusion, and topic-subtopic, could provide the missing link where genus/species or whole/part are inadequate. Distinct codes, BT/NT and whole/part, should be provided. Sorting relationships with mechanical means can only lead to confusion.