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Dagobert Soergel
College of Information Studies, University of Maryland

Thesauri for knowledge-based assistance in searching digital libraries

[Full Text PDF]

This introductory workshop is intended for anyone concerned with subject access to digital libraries. It provides a bridge by presenting methods of subject access as treated in an information studies program for those coming to digital libraries from other fields.

: Participants should
  • appreciate the complexity of subject access and understand the problems that a thesaurus can help solve.
  • understand the principles of thesaurus structure.
  • be able to apply thesaurus structure to solving subject access problems.
  • be able to identify and evaluate thesauri suitable for a specific situation defined by a user community and by the collection of a digital library.

The tutorial will elucidate through examples the conceptual and vocabulary problems users face when searching digital libraries. It will show how a well-structured thesaurus can be used as the knowledge base for an interface that can assist users with search topic clarification and with finding good search terms. It will touch on cross-database and cross-language searching as natural extensions of these functions. It will cover the thesaurus structure needed to support these functions: Concept- term relationships for vocabulary control and synonym expansion, conceptual structure for topic clarification and hierarchic query term expansion. Discussion of a few sample thesauri will illustrate these principles.


  • Detailed outline with examples (all slides) and a checklist of thesaurus evaluation criteria
  • Sample pages from selected thesauri
  • A bibliography of thesauri, especially thesauri available electronically (e.g., on the Web)


  • Problems to be solved: User orientation in a concept space and vocabulary confusion
  • Thesaurus functions
    • Conceptual map and standardized language for a field
    • Vocabulary control for indexing and searching, including free- text searching, cross-database searching, and cross-language searching
    • User-centered indexing
    • Knowledge base for user interface:
    • Assistance with search topic clarification through browsing well-structured hierarchies and guided facet analysis
    • Query term mapping and query term expansion (synonyms and hierarchic inclusion)
  • Thesaurus structure
    • Concept-term relationships
    • Conceptual structure: Semantic analysis and facets. Hierarchy
  • Examples of classifications and thesauri
    • Dewey Decimal Classification
    • Medical Subject Headings and Unified Medical Language System
    • WordNet
    • CYC Ontology
    • Alcohol and Other Drug Thesaurus
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