Networked Knowledge Organization Systems: introduction to a special issue

Linda Hill

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Networked Knowledge Representation and Exchange using UML and RDF

Stephen Cranefield

This paper proposes the use of the Unified Modeling Language (UML) as a language for modelling ontologies for Web resources and the knowledge contained within them. To provide a mechanism for serialising and processing object diagrams representing knowledge, a pair of XSLT stylesheets have been developed to map from XML Metadata Interchange (XMI) encodings of class diagrams to corresponding RDF schemas and to Java classes representing the concepts in the ontologies. The Java code includes methods for marshalling and unmarshalling object-oriented information between in-memory data structures and RDF serialisations of that information. This provides a convenient mechanism for Java applications to share knowledge on the Web.

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Semantic Problems of Thesaurus Mapping

Martin Doerr

With networked information access to heterogeneous data sources, the problem of terminology provision and interoperability of controlled vocabulary schemes such as thesauri becomes increasingly urgent. Solutions are needed to improve the performance of full-text retrieval systems and to guide the design of controlled terminology schemes for use in structured data, including metadata. Thesauri are created in different languages, with different scope and points of view and at different levels of abstraction and detail, to accommodate access to a specific group of collections. In any wider search accessing distributed collections, the user would like to start with familiar terminology and let the system find out the correspondences to other terminologies in order to retrieve equivalent results from all addressed collections. This paper investigates possible semantic differences that may hinder the unambiguous mapping and transition from one thesaurus to another. It focusses on the differences of meaning of terms and their relations as intended by their creators for indexing and querying a specific collection, in contrast to methods investigating the statistical relevance of terms for objects in a collection. It develops a notion of optimal mapping, paying particular attention to the intellectual quality of mappings between terms from different vocabularies and to problems of polysemy. Proposals are made to limit the vagueness introduced by the transition from one vocabulary to another. The paper shows ways in which thesaurus creators can improve their methodology to meet the challenges of networked access of distributed collections created under varying conditions. For system implementers, the discussion will lead to a better understanding of the complexity of the problem.

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MetaNet - A Metadata Term Thesaurus to Enable

Jane Hunter

Metadata interoperability is a fundamental requirement for access to information within networked knowledge organization systems. The Harmony international digital library project [1] has developed a common underlying data model (the ABC model) to enable the scalable mapping of metadata descriptions across domains and media types. The ABC model [2] provides a set of basic building blocks for metadata modeling and recognizes the importance of 'events' to describe unambiguously metadata for objects with a complex history. To test and evaluate the interoperability capabilities of this model, we applied it to some real multimedia examples and analysed the results of mapping from the ABC model to various different metadata domains using XSLT [3]. This work revealed serious limitations in the ability of XSLT to support flexible dynamic semantic mapping. To overcome this, we developed MetaNet [4], a metadata term thesaurus which provides the additional semantic knowledge that is non-existent within declarative XML-encoded metadata descriptions. This paper describes MetaNet, its RDF Schema [5] representation and a hybrid mapping approach which combines the structural and syntactic mapping capabilities of XSLT with the semantic knowledge of MetaNet, to enable flexible and dynamic mapping among metadata standards.

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Having the Right Connections: the LIMBER Project

Ken Miller, Brian Matthews

As with any journey, you have to make the right connections if you want to reach your desired destination. The goal in the LIMBER project is to facilitate cross-European data analysis independent of domain, resource, language and vocabulary. The paper describes the expertise, associations, standards and architecture underlying the project deliverables designed to achieve the project's ambitious aims.

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Augmenting Thesaurus Relationships: Possibilities for Retrieval

Douglas Tudhope, Harith Alani, Christopher Jones

This paper discusses issues concerning the augmentation of thesaurus relationships, in light of new application possibilities for retrieval. We first discuss a case study that explored the retrieval potential of an augmented set of thesaurus relationships by specialising standard relationships into richer subtypes, in particular hierarchical geographical containment and the associative relationship. We then locate this work in a broader context by reviewing various attempts to build taxonomies of thesaurus relationships, and conclude by discussing the feasibility of hierarchically augmenting the core set of thesaurus relationships, particularly the associative relationship. We discuss the possibility of enriching the specification and semantics of Related Term (RT relationships), while maintaining compatibility with traditional thesauri via a limited hierarchical extension of the associative (and hierarchical) relationships. This would be facilitated by distinguishing the type of term from the (sub)type of relationship and explicitly specifying semantic categories for terms following a faceted approach. We first illustrate how hierarchical spatial relationships can be used to provide more flexible retrieval for queries incorporating place names in applications employing online gazetteers and geographical thesauri. We then employ a set of experimental scenarios to investigate key issues affecting use of the associative (RT) thesaurus relationships in semantic distance measures. Previous work has noted the potential of RTs in thesaurus search aids but also the problem of uncontrolled expansion of query term sets. Results presented in this paper suggest the potential for taking account of the hierarchical context of an RT link and specialisations of the RT relationship.

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